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1. A boy referred to a genetics clinic was found to have 1 drumstick in blood neutrophils. The boy is likely to have the following syndrome:

Explanation

FullSizeRender (1)

krushkrok No70 (2007)

Drumstick – barr body. Barr body is an inactive X-chromosome. So a boy (XY) with an inactive X-chromosome must have an additional X-chromosome – XXY (Klinefelter’s syndrome). Causes :

* nondisjunction (maternal and paternal nondisjunction in meiosis I)

* Mosaicism: with the karyotype being 46, XY/47, XXY

Manifestations: gynecomastia, female pattern of pubic hair distribution, no facial hair, high voice.

2.

A 26-year-old female consulted a doctor about having stool with white flat moving organisms resembling noodles. Laboratory analysis revealed proglottids with the following characteristics: long, narrow, with a longitudinal channel of the uterus with 17-35 lateral branches on each side. What kind of intestinal parasite was found?

Explanation

krushkrok No22 (2014)

Taeniarhynchus saginatus (Taenia saginata) is a tapeworm. An intestinal parasite. It can be differentiated from other tapeworms by the number of uterine branches. Taenia saginata has 15 – 25 uterine branches, while other species such as Taenia solium have 5-12. Humans are infected by eating raw or undercooked beef containing larvae.

3.

Amniocentesis revealed two sex chromatin bodies (Barr bodies) in each cell of the sample. What disease is this character typical for?

Explanation

Barr body is an inactive X-chromosome. A normal female has one barr body XX, a normal male has no barr body XY.

Trisomy XXXX (only one X is active in a female; therefore, 2 barr bodies)

KlinefelterXXY (one barr body)

Turner’s – XO (no barr body)

Down and Patau involves autosomal chromosomes and not sex chromosomes.

4. An 18-year-old male has been diagnosed with Marfan syndrome. Examination revealed a developmental disorder of connective tissue and eye lens structure, abnormalities of the cardiovascular system, arachnodactylia. What genetic phenomenon has caused the development of this disease?

Explanation

* Pleiotropy: one gene contributes to multiple phenotypic effects → disorder of connective tissue and eye lens structure, abnormalities of CNS, arachnodactylia. Marfan is FBN1 gene mutation on chromosome 15; Marfan is one gene defect causing all this phenotypic defects.

* Codominance: both alleles contribute to the phenotype of the heterozygote. e.g. blood group AB

* Incomplete dominance: intermediate inheritance. Red + White → Pink

* Multiple allelism e.g. ABO blood type

5.

A female patient saught medical-genetic consultation. Physical examination revealed pterygium colli deformity (webbed neck), broad chest, underdeveloped breasts. Study of buccal epithelium cells revealed no X-chromatin in the nuclei. This indicates that the patient has the following syndrome:

Explanation

These characterize Turner’s syndrome (XO). It can be complete monosomy (45,XO) or mosaicism (e.g. 45,XO/46,XX). Klinefelter is related to males. The rest are not related to sex chromosomes, but they are autosomes.

6.

When defining blood group according to the ABO system, using salt solutions of monoclonal antibodies, agglutination didn’t occur with any of the solutions. What blood group is it?

Explanation

Blood group O(I): no antigens, therefore no agglutination. 

Blood group A(II): A antigen, agglutinate with blood group B(III) and O(I).

Blood group B(III): B antigen, agglutinate with blood group A(II) and O(I).

Blood group AB(IV): A and B antigen, agglutinate with all blood groups. No antibody.

Blood group name is determined by the antigen present on RBC, but the patient has an opposite antibody. So whenever, the antibody corresponds to the antigen, there is agglutination. Since O does not have any antigen, no agglutination can occur.

7.

A female suffered rubella during pregnancy. The child was born with developmental abnormalities, namely cleft lip and palate. The child’s genotype is normal. These malformations are a manifestation of:

Explanation

Variability represents the propriety of an organism to gain new traits, different from those of their parents. Variations may be induced by internal factors (hormones, metabolites) and external factors (physical, chemical and biological). The main biological factors are viruses (rubella virus), bacterial and fungal toxins. Types of variability: hereditary (genotypic) and Non-hereditary (phenotypic, modification). Non-hereditary/Modification variability: different factors (e.g. rubella virus in the question) may change the phenotype, without modifying the DNA i.e. does not affect the genotype. Hereditary on the other hand can be caused by mutations in the DNA.

8.

During cell division, DNA replication occurs by a signal from the cytoplasm, and a certain portion of the DNA helix unwinds and splits into two individual strains. What enzyme facilitates this process?

Explanation

*Helicase unwinds DNA template at the replication fork.

*DNA-dependent RNA polymerase (primase) makes an RNA primer on which DNA polymerase III can initiate replication.

*Ligase seals fragments of newly synthesized DNA fragments (i.e. joins okazaki fragments).

*DNA polymerase III elongates leading strand and lagging strand. DNA polymerase I degrades RNA primer, replaces it with DNA.

9.

As an example of specific human parasites one can name Plasmodium falciparum, human pin worm and some others. The source of parasite invasion is always a human. Such specific human parasites cause the diseases that are called:

Explanation

Anthroponoses: diseases transmissible from human to human. Zoonoses: diseases transmissible from living animals to humans; formerly called anthropozoonoses. And diseases transmissible from humans to animals are called zooanthroponoses.

10. The organisms to be identified have a nucleus surrounded by a nuclear membrane. Genetic material is concentrated predominantly in the chromosomes which consist of DNA strands and protein molecules. These cells divide mitotically. Identify these organisms:

Explanation

The fundamental difference between eukaryotes and prokaryotes is that eukaryotes do have ‘true’ nuclei containing their DNA, whereas the genetic material in prokaryotes is not membrane-bound. Eukaryotes contain multiple linear chromosomes with large amount of noncoding and repetitive DNA.

11.

A 2-year-old boy is diagnosed with Down syndrome. What chromosomal changes may be the cause of this disease?

Explanation

Chromosomal disorders: trisomy 21 (down’s syndrome); trisomy 18 (edward’s syndrome); trisomy 13 (patau’s syndrome); monosomy X (turner’s syndrome-XO); trisomy X (XXX);

Normal female (XX); normal male (XY)

12.

An underage patient has signs of achondroplasia (dwarfism). It is known that this is a monogenic disease and the gene that is responsible for the development of such abnormalities is a dominant one. The development of that child’s brother is normal. Specify the genotype of the healthy child:

Explanation

A – gene for achondroplasia dwarfism

        a – normal gene

AA (homozygous) and Aa (heterozygous) will express the disease because the gene controlling the disease is dominant.

Only a recessive homozygous gene (aa) can express the normal phenotype

13.

Examination of the duodenal contents revealed some pear-shaped protozoa with two nuclei and four pairs of flagella. The organisms had also two axostyles between the nuclei and a ventral adhesive disc. What protozoan representative was found in the patient?

Explanation

Giardia lamblia is pear shape or “clownface” with two nuclei, 4 pairs of flagella. The two nuclei are outlined by adhesive discs. Transmitted by cysts in water. The cysts are oval, have 4 nuclei and have clearly visible axostyles. It causes Giardiasis – bloating, flatulence, foul-smelling, fatty diarrhea. Diagnosis: trophozoites or cysts in stool.

14.

A  man  suffering  from  a hereditary disease  married a healthy  woman.  They got  5 children,  three  girls and  two  boys. All  the  girls  inherited their  father’s  disease. What is the type of the disease inheritance?

Explanation

           X-linked dominant: it can be transmitted through both parents. Mothers transmit to 50% of daughters and sons; fathers transmit to all daughters but no son (father-daughters; no generation is left out).

X-linked recessive: sons of heterozygous mothers have a 50% chance of being affected. No male-to-male transmission. Recessive genetic diseases skips generations.

Autosomal dominant and recessive 

Y-linked: father to all sons; no female involvement (mother or daughter)

15. A couple  has a son with haemophilia. The parents are healthy  but the maternal grandfather also has haemophilia. Specify the type of inheritance:

Explanation

Autosomal dominant: often due to defects in structural genes. Many generations, both male and female are affected. Found in every generation; no generation is left out (skipped). Parent – child in every generation.

Autosomal recessive is usually seen in some generations (other generations are skipped).

It is sex linked, if only males or only females(X-linked) are affected.

     Recessive because a generation was left out (skipped- grandfather to son); it is sex linked because its from grandfather to son (only the male is involved).

16.

Examination  of  newborns   in  one  of the  Ukrainian cities revealed  a baby  with phenylketonuria. The baby’s parents don’t  suffer  from  this  disease  and  have two    other     healthy    children.    Specify the most likely parents’ genotype with phenylketonuria gene:

Explanation

              Aa X Aa

AA  Aa  Aa  aa

AA-healthy (25%)

Aa-carriers (heterozygous; 50%)

aa-sick with hemophilia (25%)

Option B will not produce a sick child.

Option C: all children will be sick.

Option D: 50% of children are carriers; the other 50% have hemophilia

Option E: 75% are healthy; 25% has hemophilia

17.

Patients with similar complaints  applied to the doctor: weakness, pain in the intestines, disorder of GIT.  Examination of the faeces revealed that one patient with four nucleus  cysts should  be hospitalized  immediately.   For what  protozoa are such cysts typical?

 

Explanation

       Entamoeba histolytica is a protozoa causing gastrointestinal infections, which can lead to amebic dysentery or liver abscess. It is transmitted by its cysts in water. It is diagnosed by stool samples or serological methods: trophozoites (with RBCs in the cytoplasm) or cysts (with up to 4 nuclei) in stool.

18.

A female patient consulted a physician about digestive disorder, extended abdominal pain. Examination revealed drastic decrease in hemoglobin concentration. It is known from the anamnesis that while living in the Far East the patient used to eat freshly-salted caviar. Some relatives  living with her had the similar condition. What  is the most likely diagnosis?

Explanation

·        Diphyllobothrium latum causes diphyllobothriasis. A fish tapeworm. In contrast to the other cestodes, which have suckers , the scolex of D. latum has two elongated sucking grooves by which the worm attaches to the intestinal wall. Infection by D. latum causes little damage in the small intestine. In some individuals, megaloblastic anemia occurs as a result of vitamin B12 deficiency caused by preferential uptake of the vitamin by the worm. Transmission: ingestion of larvae from raw freshwater fish. Caviar is prepared from fish.

·        Echinococcus granulosus causes Echinococcosis. It is composed of a scolex and only 3 proglottids, making it one of the smallest tapeworms. The scolex has a circle of hooks and 4 suckers similar to Taenia solium. Dogs are the most important definitive hosts. The intermediate hosts are usually sheep. Humans are almost always dead-end intermediate hosts. Transmission: ingestion of eggs from dog faeces. Disease – hydatid cysts in liver causing anaphylaxis if antigens released.

·        Taeniasis: there are two important human pathogens in the genus Taenia: T. solium (pork tapeworm) and T. saginata (beef tapeworm)

·        Trichiniasis (Trichinosis) is caused by Trichinella spiralis (nematode- roundworm). Transmission: fecal-oral; undercooked meat (especially pork). A few days after eating undercooked meat, usually pork, the patient experiences diarrhea followed by 1-2weeks later by fever, muscle pain, periorbital edema and eosinophilia.

·        Ascaridiasis (Ascariasis) caused by Ascaris lumbricoides (giant roundworm). The major damage occurs during larval immigration rather than from the presence of the adult worm in the intestines. The principal sites of tissue reaction are the lungs, where inflammation with an eosinophilic exudates occurs in response to larval antigens. Ascaris pneumonia with fever, cough and eosinophilia can occur with a heavy larval burden.

19. 46 chromosomes were revealed on karyotype examination of the  5 year  old girl. One of the 15th pair of chromosomes is longer than usual due to connected chromosome from the 21 pair. What type of mutation does this girl have?

Explanation

       Translocations occur when two chromosome regions join together, when they would not normally. Chromosome translocations in somatic cells may be associated with tumorogenesis. We can have reciprocal and robertsonian translocations. Examples of diseases due to translocations are: Burkitt lymphoma t(8:14); Chronic myelogenous leukemia t(9;22) – Philadelphia chromosome.

Duplications occur when a portion of the chromosome is present on the chromosome in two copies.

Inversion involve an end-to-end reversal of a segment within the same chromosome (turn of 180o).

Deletion is a mutation in which a part of a chromosome or a sequence of DNA is missing. Deletion is the loss of genetic material.

20. During a prophylactic medical examination   a  7-year-old   boy  was  diagnosed with  daltonism.   His parents are  healthy and have normal colour vision, but his grandfather on his mother’s side has the same abnormality. What is the type of the abnormality inheritance?

Explanation

Autosomal dominant: often due to defects in structural genes. Many generations, both male and female are affected. Found in every generation; no generation is left out (skipped). Parent – child in every generation.

Autosomal recessive is usually seen in some generations (other generations are skipped).

It is sex linked, if only males or only females(X-linked) are affected.

Parents are healthy. Grandfather –Boy. A generation was left out (skipped).

21.

It is known that the gene responsible for development of blood groups according to  AB0  system  has  three  allele  variants. If a man has IV blood group, it can be explained by the following variability form:

Explanation

             Type IV blood group – AB

Combinative because both alleles of this gene are equally expressed in dominant forms and there is no masking of the characteristics (phenotype) of any of the allele.

22. According to the phenotypic diagnosis  a female  patient has been  provisionally diagnosed with X-chromosome polysomia.  This  diagnosis  can  be  confirmed by a cytogenetic  method.  What karyotype will allow  to  confirm  the  diagnosis?

Explanation

46 XX is a normal female sex chromosome. All other options are karyotypes for male patients because of the Y chromosome.

Barr body is an inactive X-chromosome. A normal female has one barr body XX, a normal male has no barr body XY.

Trisomy XXXX (only one X is active in a female; therefore, 2 barr bodies; polysomia)

KlinefelterXXY (one barr body)

Turner’s – XO (no barr body)

Normal female - XX (one barr body)

23.

A patient complains  of skin itch, especially between fingers, in the inguinal creases,  on  the  lower  abdomen. Examination   of  these   regions   revealed   there some small vesicles. Laboratory diagnostics allowed to establish  that  this condition had  been  caused  by  a  representative of Arthropoda. Specify  the  disease  caused by this arthropod:

Explanation

Scabies is a contagious skin disease caused by the itch mite – Sarcoptes scabiei. A person may become infected either by direct contact with a sick individual (including sexual contact) or by indirect one (when the bed clothes, underwear or bed is shared). Commonly the skin eruptions are localized on the interdigital folds of hands, on the lateral surfaces of fingers, flexible surfaces of wrist joint, on the skin of forearms, shoulders, chest, abdomen, buttocks and thighs. Itching is the first and essential symptom of scabies. The pruritic lesions result from a delayed hypersensitivity reaction to the faeces of the mite. The mite is located within the stratum corneum of the epidermis. At the sites of entry and exit of mites double morphologic elements of rash, more often microvesicles, papules, blisters or pustules, multiple scratches and excoriations and small sanguinolent crusts are formed.

24.

Cytogenetic examination of  a  patient  with dysfunction  of the  reproductive system revealed  normal  karyotype 46,ХУ in some cells, but most cells have Klinefelter’s syndrome  karyotype - 47,ХХУ. Such phenomenon of cell inhomogeneity is called:

Explanation

Barr body is an inactive X-chromosome. So a boy (XY) with an inactive X-chromosome must have an additional X-chromosome – XXY (Klinefelter’s syndrome). Causes :

* nondisjunction (maternal and paternal nondisjunction in meiosis I)

* Mosaicism: with the karyotype being 46, XY/47, XXY

Manifestations: gynecomastia, female pattern of pubic hair distribution, no facial hair, high voice.

25.

Life   cycle   of   a   cell   includes   a process   of  DNA   autoreduplication.  As a result of this process monochromatid chromosomes become  bichromatid. This phenomenon is observed within the following period  of the cell cycle:

Explanation

Somatic cell division is a cyclic process divided into two phases: mitosis (M phase) and interphase. Three other phases, Gap 1 (G1); synthesis phase (S) and Gap 2 (G2) further subdivide interphase. M phase is followed by G1.

M phase: karyokinesis – division of the nucleus into two daughter nuclei.

                  Cytokinesis – division of the cell into two daughter cells.

G1: a period in which no DNA synthesis occurs. Period of cell growth S or DNA synthesis phase follows G1 phase. The DNA of the cell is doubled. The S phase is followed by a period in which no DNA synthesis occurs, a second gap or G2 phase. A cell that leaves the cycle in G1 phase to begin “terminal” differentiation enters the G0 phase, (“O” stands for “outside” the cycle).

26.

A cell at the stage of mitosis anaphase was stimulated by colchicine  that  inhibits  chromosome separation  to  the  poles. What type of mutation will be caused?

Explanation

When separation does not occur, it is called non-disjunction and both members of a pair of homologous chromosome move into one cell. In mitotic non-disjunction, mosaicism is produced with some cells having an abnormal chromosome number and others being normal; an extra chromosome is present (trisomy – polysomy - polyploidy) or one is missing (monosomy). Polyploidy occurs when the entire chromosome set is present in more than two copies, so the individual may be triploid rather than diploid and have a chromosome number of 69.
27.

Examination  of  duodenal contents revealed   some   pyriform   protozoa  with twin  nuclei   and   four   pairs   of  flagella. There  were two supporting filaments between the  nuclei  and  a  suctorial  disc on  the  ventral  side. What  representative of protozoa was revealed  in this patient?

Explanation

Giardia lamblia is pear shape or “clownface” with two nuclei, 4 pairs of flagella. The two nuclei are outlined by adhesive discs. Transmitted by cysts in water. The cysts are oval, have 4 nuclei and have clearly visible axostyles. It causes Giardiasis – bloating, flatulence, foul-smelling, fatty diarrhea. Diagnosis: trophozoites or cysts in stool.

28.

A shepherd who has tended sheep together with dogs consulted a doctor about pain  in  his right  subcostal area, nausea, vomiting. Roentgenoscopy revealed a tumour-like formation. What kind of helminthiasis might be suspected?

Explanation

·        Echinococcus granulosus causes Echinococcosis. It is composed of a scolex and only 3 proglottids, making it one of the smallest tapeworms. The scolex has a circle of hooks and 4 suckers similar to Taenia solium. Dogs are the most important definitive hosts. The intermediate hosts are usually sheep. Humans are almost always dead-end intermediate hosts. Transmission: ingestion of eggs from dog faeces. Disease – hydatid cysts in liver causing anaphylaxis if antigens released.

·        Diphyllobothrium latum causes diphyllobothriasis. A fish tapeworm. In contrast to the other cestodes, which have suckers , the scolex of D. latum has two elongated sucking grooves by which the worm attaches to the intestinal wall. Infection by D. latum causes little damage in the small intestine. In some individuals, megaloblastic anemia occurs as a result of vitamin B12 deficiency caused by preferential uptake of the vitamin by the worm. Transmission: ingestion of larvae from raw freshwater fish. Caviar is prepared from fish.

·        Taeniasis: there are two important human pathogens in the genus Taenia: T. solium (pork tapeworm) and T. saginata (beef tapeworm)

·        Trichiniasis (Trichinosis) is caused by Trichinella spiralis (nematode- roundworm). Transmission: fecal-oral; undercooked meat (especially pork). A few days after eating undercooked meat, usually pork, the patient experiences diarrhea followed by 1-2weeks later by fever, muscle pain, periorbital edema and eosinophilia.

·        Ascaridiasis (Ascariasis) caused by Ascaris lumbricoides (giant roundworm). The major damage occurs during larval immigration rather than from the presence of the adult worm in the intestines. The principal sites of tissue reaction are the lungs, where inflammation with an eosinophilic exudates occurs in response to larval antigens. Ascaris pneumonia with fever, cough and eosinophilia can occur with a heavy larval burden.

29.

Sex chromosomes of a woman didn’t separate and  move  to the  opposite  poles of a cell during  gametogenesis (meiosis). The ovum was impregnated with a normal spermatozoon. Which chromosomal disease can be found in her child?

Explanation

In meiosis, two members of a pair of homologous chromosomes normally separate during the first meiotic division, so that each daughter cell receives one member of each pair. Sometimes, however, separation does not occur (nondisjunction) and both members of a pair move into one cell. As a result of nondisjunction of the chromosomes, one cell receives 24 chromosomes and the other receives 22 instead of the normal 23. When at fertilization, a gamete having 23 chromosomes (spermatozoon) fuses with a gamete having 24 or 22 chromosomes, the result is an individual with either 47 chromosomes (47 XXX – trisomy X) or 45 chromosomes (45 XO – monosomy X, Turner’s syndrome). In women, the incidence of chromosomal abnormalities including nondisjunction, increases with age especially at 35years and older.

30.

Examination  of  an 18-year-old girl revealed the following features: hypoplasia of  the  ovaries,  broad shoulders, narrow pelvis, shortening of the lower extremities, \\\"sphinx  neck\\\".  Mental development is normal. The girl was diagnosed with Turner’s  syndrome. What kind of chromosome abnormality is it?

Explanation

These characterize Turner’s syndrome (XO). It can be complete monosomy (45,XO) or mosaicism (e.g. 45,XO/46,XX).

In meiosis, two members of a pair of homologous chromosomes normally separate during the first meiotic division, so that each daughter cell receives one member of each pair. Sometimes, however, separation does not occur (nondisjunction) and both members of a pair move into one cell. As a result of nondisjunction of the chromosomes, one cell receives 24 chromosomes and the other receives 22 instead of the normal 23. When at fertilization, a gamete having 23 chromosomes (spermatozoon) fuses with a gamete having 24 or 22 chromosomes, the result is an individual with either 47 chromosomes (47 XXX – trisomy X) or 45 chromosomes (45 XO – monosomy X, Turner’s syndrome). In women, the incidence of chromosomal abnormalities including nondisjunction, increases with age especially at 35 years and older.

31.

Hypertrichosis  is  the  Y-linked character. The  father  has  hypertrichosis, and  the  mother is healthy.  In  this  family, the  probability of having  a child with hypertrichosis is:

Explanation

Hypertrichosis is  Y-linked, therefore all the male child will have this pathology. The probability of having a male child is 50% (0.5). Since,all the male child of this man have the pathology,it therefore means that the probability of inheriting this pathology (hypertrichosis) is 50% or 0.5

32.

A  35-year-old  male  patient has been referred by an andrologist for the genetic counselling  for  the  deviations  of  physical and mental  development. Objectively: the patient is tall, has asthenic  constitution, gynecomastia, mental retardation. Microscopy of the oral mucosa cells revealed sex chromatin (single Barr  body)  in 30% of cells. What is the most likely diagnosis?

Explanation

Barr body is an inactive X-chromosome. So a boy (XY) with an inactive X-chromosome must have an additional X-chromosome – XXY (Klinefelter’s syndrome). Causes :

* nondisjunction (maternal and paternal nondisjunction in meiosis I)

* Mosaicism: with the karyotype being 46, XY/47, XXY

Manifestations: gynecomastia, female pattern of pubic hair distribution, no facial hair, high voice.

33.

Healthy parents  with  unremarkable family history  have  the  child with multiple developmental defects. Cytogenetic analysis revealed  the trisomy 13 in the somatic  cells (Patau syndrome). What phenomenon has caused the defects?

Explanation

In preparation for fertilization, germ cells undergo gametogenesis, which includes meiosis, to reduce the number of chromosomes. Chromosomal abnormalities may be numerical or structural. Abnormalities in chromosome number may originate during meiotic or mitotic divisions. In meiosis, two members of a pair of homologous chromosomes normally separate during the first meiotic division, so that each daughter cell receives one member of each pair. Sometimes, however, separation does not occur (nondisjunction) and both members of a pair move into one cell. As a result of nondisjunction of the chromosomes, one cell receives 24 chromosomes and the other receives 22 instead of the normal 23. When at fertilization a gamete having 23 chromosomes fuses with a gamete having 24 or 22 chromosomes, the result is an individual with either 47 chromosomes (e.g.trisomy 13, 18,21, klinefelter) or 45 chromosomes (monosomy – 45 XO turner’s syndrome). Nondisjunction which occurs during either the first or the second meiotic division of the germ cells, may involve the autosomes (trisomy 13,18,21) or sex chromosomes (turner’s and klinefelter’s syndrome).

If nondisjunction occurs during mitosis (mitotic nondisjunction) – such conditions produce mosaicism, with some cells having an abnormal chromosome number and others being normal. Therefore abnormal gametogenesis can produce nondisjunction.

34.

A  pregnant woman  underwent AB0 blood typing. Red blood cells were agglutinated with  standard sera  of the  I and II blood groups, and were not agglutinated  with the  III  group  serum.  What  is the patient’s blood group?

Explanation

Blood group O(I): no antigens, therefore no agglutination.

Blood group A(II): A antigen, agglutinate with blood group B(III) and O(I).

Blood group B(III): B antigen, agglutinate with blood group A(II) and O(I).

Blood group AB(IV): A and B antigen, agglutinate with all blood groups. No antibody.

Blood group name is determined by the antigen present on RBC, but the patient has an opposite antibody. So whenever, the antibody corresponds to the antigen, there is agglutination. Since O does not have any antigen, no agglutination can occur.

35.

Mother of  a boy  who  had  recently returned  from   a  summer   camp   found some  small  whitish  insects  up  to  3 mm long  on  the  child’s clothing.  Specify  the parasite:

Explanation

Pediculus humanus humanus (body or clothes louse). The insect was found on the clothing.

36.

A mother had  taken  synthetic hormones  during   pregnancy.   Her daughter was born with hirsutism formally resembling  of adrenal syndrome.  Such manifestation of variability is called:

Explanation

Phenocopy is an environmentally induced phenotype mimicking one usually produced by a specific genotype. An individual exhibiting such a phenotype; the simulated trait is a phenocopy. The phenotype hirsuitism mimics adrenal syndrome.
37.

Students  study the stages of gametogenesis. They  analyze  a cell having  a  haploid   number   of  chromosomes, and each chromosome consists of two chromatids. The chromosomes are located in the equatorial plane of the cell. Such situation is typical for the following stage of meiosis:

Explanation

Gametogenesis involves the generation of germ cells (gametes) through meiosis. Meiosis requires 2 cell divisions, meiosis I and II, in order to reduce the number of chromosomes to the haploid number of 23. At the beginning of meiosis I, germ cells replicate their DNA so that each of the 46 chromosomes is duplicated into sister chromatids. Homologous pairs then separate into two daughter cells, thereby reducing the chromosome number from diploid to haploid. Shortly thereafter, meiosis II separates sister chromatids (2 sister chromatids are joined in the middle by a centromere). Each gamete then conatins 23 chromosomes.

Metaphase is a stage of cell division in which chromosomes are at their most condensed and coiled stage and chromosomes are arranged along the equatorial plane during this phase. Cell division is usually studied during this phase.

38.

A   specimen   of  an   onion   rootlet includes  a  cell  in  which  the  fully condensed  chromosomes are  located   in the equatorial plane making the monaster. What phase of the mitotic cycle is the cell in?

Explanation

Gametogenesis involves the generation of germ cells (gametes) through meiosis. Meiosis requires 2 cell divisions, meiosis I and II, in order to reduce the number of chromosomes to the haploid number of 23. At the beginning of meiosis I, germ cells replicate their DNA so that each of the 46 chromosomes is duplicated into sister chromatids. Homologous pairs then separate into two daughter cells, thereby reducing the chromosome number from diploid to haploid. Shortly thereafter, meiosis II separates sister chromatids (2 sister chromatids are joined in the middle by a centromere). Each gamete then conatins 23 chromosomes.

Metaphase is a stage of cell division in which chromosomes are at their most condensed and coiled stage and chromosomes are arranged along the equatorial plane during this phase. Cell division is usually studied during this phase.

 
39.

A patient consulted a physician about chest pain, cough, fever. Roentgenography of lungs revealed  eosinophilic infiltrates which were found to contain  the  larvae.  What  kind  of helminthiasis   are   these   presentations  typical for?

 

Explanation

Ascaris lumbricoides (giant roundworm) is the causative agent of Ascariasis. Transmission: fecal-oral; eggs are visible in faeces under microscope. Some patients may have pulmonary symptoms or neurological disorders during migration of the larvae. A bolus of worms may obstruct the intestine; migrating larvae may cause pneumonitis and eosinophilia.

Ascaridiasis (Ascariasis) caused by Ascaris lumbricoides (giant roundworm). The major damage occurs during larval immigration rather than from the presence of the adult worm in the intestines. The principal sites of tissue reaction are the lungs, where inflammation with an eosinophilic exudates occurs in response to larval antigens. Ascaris pneumonia with fever, cough and eosinophilia can occur with a heavy larval burden.

40.

Analysis of the family history of children with Van der Woude syndrome revealed  that  in their  families one  of the parents had the typical for this syndrome defects   (cleft lip and palate, lip pits regardless of  gender). What  is the  type of inheritance of this syndrome?

Explanation

Autosomal dominant: often due to defects in structural genes. Many generations, both male and female are affected. Found in every generation; no generation is left out (skipped). Parent – child in every generation.

Autosomal recessive is usually seen in some generations (other generations are skipped).

It is sex linked, if only males or only females(X-linked) are affected.

41.

Medical   examination  at   the   military registration and enlistment office revealed   that  a  15-year-old  boy  was  high, with eunuchoid body proportions, gynecomastia,  female   pattern  of  pubic hair distribution. The boy had also fat deposits  on the  thighs,  no facial hair,  high voice, subnormal intelligence  quotient. Which karyotype corresponds with this disease?

 

Explanation

Barr body is an inactive X-chromosome. So a boy (XY) with an inactive X-chromosome must have an additional X-chromosome – XXY (Klinefelter’s syndrome). Causes :

* nondisjunction (maternal and paternal nondisjunction in meiosis I)

* Mosaicism: with the karyotype being 46, XY/47, XXY

Manifestations: gynecomastia, female pattern of pubic hair distribution, no facial hair, high voice.

42.

One  of  the  parents is  suspected   of having phenylketonuria recessive gene. What  is the  risk of giving birth  to a child with inborn  phenylketonuria?

Explanation

         Only one of the parents has a recessive gene

   AA        Aa crossing

AA  Aa    AA Aa

All the children are healthy (0%)

Phenylketonuria is a recessive genetic defect and it needs to be homozygous recessive (aa) to be expressed.

43.

While  studying  maximally  spiralized chromosomes of human karyotype the process of cell division was stopped in the following phase:

Explanation

Metaphase is a stage of cell division in which chromosomes are at their most condensed and coiled stage and chromosomes are arranged along the equatorial plane during this phase. Cell division is usually studied during this phase.

44.

A patient consulted  an urologist about pain during urination. Analysis of his urine taken  in the daytime  revealed  eggs with a characteristic sharp point. It is known from  the  anamnesis that  the  patient has recently  returned from Australia. What is the most likely diagnosis?

Explanation

The most important trematodes (flukes) are Schitosoma species (blood flukes). Schistosoma causes Schistosomiasis. Schistosoma mansoni and Schistosoma japonicum affect the GIT, whereas Schistosoma haematobium affects the urinary tract. Schistosoma haematobium’s eggs have a terminal spine (sharp point) and lives in the veins draining the urinary bladder. Schistosoma haematobium is found in Africa and the middle-east. Diagnosis depends on finding the characteristic ova (egg) in faeces or urine.

45.

Before  a surgery a blood sample of a 30-year-old  man  has  been  typed.  Blood is Rh-positive. Standard  serums  of  such groups as 0 αβ (I), Аβ (II), Вα (III) didn’t activate  erythrocyte agglutination reaction. The group of the analyzed blood is:

Explanation

Blood group O(I): no antigens, therefore no agglutination.

Blood group A(II): A antigen, agglutinate with blood group B(III) and O(I).

Blood group B(III): B antigen, agglutinate with blood group A(II) and O(I).

Blood group AB(IV): A and B antigen, agglutinate with all blood groups. No antibody.

Blood group name is determined by the antigen present on RBC, but the patient has an opposite antibody. So whenever, the antibody corresponds to the antigen, there is agglutination. Since O does not have any antigen, no agglutination can occur.

46.

A patient working at a pig farm complains    about    paroxysmal    abdominal pain,  liquid  feces with admixtures of mucus and blood, headache, weakness, fever. Examination of large intestine revealed  ulcers  from 1 mm up to several cm large, feces contained oval unicellular organisms  with cilia. What disease should be suspected?

 

Explanation

        Balantidium coli cause balantidiasis. It is the only ciliated protozoan that causes human disease i.e. diarrhea. Domestic animals, especially pigs are the main reservoir for the organism and humans are infected after ingesting the cysts in food or water contaminated with animal or human faeces. Diagnosis is made by finding large ciliated trophozoites or large cysts with a characteristic V-shaped nucleus in the stool. The trophozoites excyst in the small intestine, travel to the colon (large intestine) and by burrowing into the wall cause an ulcer similar to that of Entamoeba histolytica.

47.

It  was  found  out  that  some compounds, for instance  fungi toxins and some  antibiotics   can  inhibit   activity  of RNA-polymerase.  What  process  will be disturbed in a cell in case of inhibition  of this enzyme?

Explanation

     The process of transcription of a typical gene can be divided into 3 phases: initiation, elongation and termination. The process of transcription begins with the binding of the RNA polymerase holoenzyme to a regionof the DNA known as the promoter. RNA polymerase is a multisubunit enzyme that recognizes a nucleotide sequence (the promoter region) at the beginning of a length of DNA that is to be transcribed. It makes a complementary RNA copy of the DNA template strand and then recognizes the end of the DNA sequence to be transcribed (the termination region).

48.

Examination of a 12-year-old boy with developmental lag revealed achondroplasia: disproportional constitution  with  evident  shortening of  upper and lower limbs as a result of growth disorder of epiphyseal cartilages  of long tubal bones. This disease is:

Explanation

         X-linked dominant: it can be transmitted through both parents. Mothers transmit to 50% of daughters and sons; fathers transmit to all daughters but no son (father-daughters; no generation is left out).

X-linked recessive: sons of heterozygous mothers have a 50% chance of being affected. No male-to-male transmission. Recessive genetic diseases skips generations.

Y-linked: father to all sons; no female involvement (mother or daughter)

Autosomal dominant: often due to defects in structural genes. Many generations, both male and female are affected. Found in every generation; no generation is left out (skipped). Parent – child in every generation.

Autosomal recessive is usually seen in some generations (other generations are skipped).

It is sex linked, if only males or only females(X-linked) are affected.

49.

A  28-year-old   female  patient consulted a  gynecologist   about   sterility. Examination revealed  underdeveloped ovaries and uterus,  irregular menstrual cycle. Analysis of the sex chromatin revealed  2 Barr’s bodies  in most  somatic cells. What  chromosome disease  is most likely?

Explanation

Barr body is an inactive X-chromosome. A normal female has one barr body XX, a normal male has no barr body XY.

Trisomy XXXX (only one X is active in a female; therefore, 2 barr bodies)

KlinefelterXXY (one barr body)

Turner’s – XO (no barr body)

50.

On  an  electron   micrograph  a  scientist  has  identified   a  structure  formed by  eight  histone  proteins and  a  part  of DNA molecule which makes about 1,75 revolutions around the molecules.  Which structure has been identified?

Explanation

          Genes are contained in a complex of DNA and proteins (mostly histones) called chromatin and its basic unit of structure is the nucleosome. Each nucleosome is composed of an octamer (8) of histone proteins and approximately 140 base pairs of DNA. Nucleosomes themselves are joined into clusters by binding of DNA existing between nucleosomes (linker DNA) with other histone proteins. Nucleosomes keep the DNA tightly coiled such that it cannot be transcribed.

51.

A male patient has fever and enanthesis.  As   a  result   of  the   examination  involving  serological  tests  he  has been  diagnosed  with fasciola hepatica. It was found  out  that  the  patient had  been infected  through  raw river  water.  Which stage  of fasciola  life cycle is invasive  for humans?

Explanation

           Clonorchis sinensis causes Clonorchiasis (asian liver fluke infection). Humans are infected by eating raw or undercooked fish containing the encysted larvae (metacercariae). After excystation in the duodenum, immature flukes enter (invade) the biliary ducts and differentiate into adults (adolescaria). The hermaphroditic adults produce eggs which are excreted in the faeces. Upon reaching fresh water, the eggs are ingested by snails which are the first intermediate hosts. The eggs hatch within the gut and differentiate first into larvae (rediae) and then into many free-swimming cercariae. Cercariae encyst under the scales of certain freshwater fish (second intermediate hosts) which are then eaten by humans.

52.

A  patient  presents with  acne  and inflammatory alterations  of  facial  skin. Microscopial   investigation of  lesion  foci has  revealed   live  arthropods  sized  0,2-0,5  mm.  They  have  prolate  vermiform form and four pairs of thin short limbs located  in  the  middle  part  of  the  body. The revealed  arthropods cause:

Explanation

         Demodex folliculorum and Demodex brevis: they are species of face mite. When large numbers of D. folliculorum are found in humans, the infestation is known as Demodicosis. D. folliculorum is semi-transparent elongated organism consisting of a head, neck, body and tail. As an adult, it can measure 0.1-0.4mm in length and possess 4 pairs of short legs near its head and neck region. In the course of time, because of chronic progradient course, pathologic process results in formation of inflammatory nodes, infiltrates and persistent vascular dilatation. Hyperemia of facial skin and eruptions are also seen.

53.

During  regular  examination of schoolchildren it was revealed  that  a 10 year old girl had asymmetric  oval eggs with a larva in the scrape from her perianal folds. What diagnosis should be made?

Explanation

Enterobius vermicularis causes pinworm infection (enterobiasis). The life cycle is confined to humans. The infection is acquired by ingesting the worm eggs. Perianal pruritus is the most prominent symptom. Pruritus is thought to be an allergic reaction to the presence of either the adult female or the eggs. Scratching predisposes to secondary bacterial infection. In Laboratory diagnosis, the eggs are recovered from perianal skin by using the scotch tape technique and can be observed microscopically. Unlike those of other intestinal nematodes, these eggs are not found in the stools. There are no means of prevention. It is treated with mebendazole.

54. A  patient has  acne  on  his face.  Microscopic  examination of scrapings from the affected  areas  revealed  living porrect vermiform   arthropoda 0,2-0,5 mm  large with four pairs of short  extremities in the front part of their bodies. What is the laboratory diagnosis?

Explanation

           Demodex folliculorum and Demodex brevis: they are species of face mite. When large numbers of D. folliculorum are found in humans, the infestation is known as Demodicosis. D. folliculorum is semi-transparent elongated organism consisting of a head, neck, body and tail. As an adult, it can measure 0.1-0.4mm in length and possess 4 pairs of short legs near its head and neck region. In the course of time, because of chronic progradient course, pathologic process results in formation of inflammatory nodes, infiltrates and persistent vascular dilatation. Hyperemia of facial skin and eruptions are also seen.

55.

A   family   of  students  who   came from  Africa  got  a child  with  anemia  signs.   The   child   died   soon.   Examination  revealed  that  the  child’s erythrocytes have  abnormal semilunar shape.  Specify genotypes of the child’s parents:

Explanation

For the parents to survive and have a sick anemic child, they must be heterozygous i.e. they only carry a recessive anemic allele.

 A – normal gene (dominant); a – anemic gene (recessive)

            Aa       X          Aa

        AA       Aa       Aa       aa

aa – only this child will be anemic

56.

A patient working at a pig farm complains    about    paroxysmal    abdominal pain,  liquid  feces with admixtures of mucus and blood, headache, weakness, fever. Examination of large intestine revealed  ulcers from  1 mm up to several cm large, feces contained oval unicellular organisms  with cilia. What disease should be suspected?

 

Explanation

         Balantidium coli cause balantidiasis. It is the only ciliated protozoan that causes human disease i.e. diarrhea. Domestic animals, especially pigs are the main reservoir for the organism and humans are infected after ingesting the cysts in food or water contaminated with animal or human faeces. Diagnosis is made by finding large ciliated trophozoites or large cysts with a characteristic V-shaped nucleus in the stool. The trophozoites excyst in the small intestine, travel to the colon (large intestine) and by burrowing into the wall cause an ulcer similar to that of Entamoeba histolytica.

57.

Normal,  actively dividing cells of human   red  bone  marrow   are  analyzed. What  number   of  cells’  chromosomes is typical for G1 period?

 

Explanation

The G1 phase of cell cycle is usually a period of cell growth (i.e. growth of cell organelles) and may last only a few hours in a rapidly dividing cell or may last a lifetime in a nondividing cell. It is a period in which there is no DNA synthesis. It precedes (comes before) the S or DNA synthesis phase. Since there is no DNA synthesis in G1 phase, it means that the number of chromosome remains at 46, but it is doubled in the S  phase.

58.

A couple had a child with Down’s disease. Mother is 42 years old. This disease is most probably  caused  by the following impairment of prenatal development:

 

Explanation

The normal and pathologic development and growth can be divided into the following stages:

·        Progenesis: characterized by gametogenesis i.e. formation and maturation of gametes. This stage occurs before the fertilization of the ovum. Pathology of gametogenesis is called gametopathy.

·        Development after fertilization is called kymatogenesis. This intrauterine phase can be divided into:

-         Blastogenesis: from day 1 – 15 of gestation. Pathology of blastogenesis is called blastopathy.

-         Embryogenesis: from day 16 to the end of the 3rd month (75th day). Pathology of embryogenesis is called embryopathy.

-         Fetogenesis: from the 4th month of gestation to delivery (from 76th -280th day). Pathology of fetogenesis is called fetopathy.

     Gametopathy is an injury of formation and maturation of the gametes during ovo- and spermatogenesis until fertilization. The most frequent is trisomy 21 (Down’s syndrome); trisomy 13 (Patau’s syndrome), trisomy 18 (Edward’s syndrome), Klinefelter’s syndrome (XXY), Turner’s syndrome (XO).

59.

An  alcoholic  woman  has born  a girl with mental  and  physical  developmental lag. Doctors diagnosed the girl with fetal alcohol syndrome. What effect is the cause of the girl’s state?

Explanation

Intoxication with drugs leads to:

·        Disturbances in organs and systems functions: neurotoxic, hepatotoxic, nephrotoxic, hematotoxic, ulcerogenous – ulcers formation in GIT.

·        Teratogenic: ability to cause fetal malformation (in the first trimester of pregnancy i.e. till 12 weeks.

·        Embryo and fetotoxic: ability to make a toxic influence on embryo and fetus correspondingly, causing disturbance down to death (after 12 weeks).

·        Mutagenic: ability to impact on a genetic level causing mutations in several generations.

·        Blastogenic: ability to cause neoplasms both benign and malignant (carcinogenic).

Mental and physical development lag; fetal alcohol syndrome are fetal malformations.

60.

A  doctor  revealed  tissues  injury  on patient’s   scalp  with  localized  suppurations and diagnosed his disease  as myiasis. This infestation is caused by larvae of the following insect:

Explanation

Myiasis is a parasitogenic infection caused by larvae of dipterous (double-wing) insects (gadflies) – Dermatobia hominis. It occurs in persons, who have come from the central and South America. The 3 major species of obligate parasitic fly larvae found in wound myiasis are the Cochliomyia hominovorax (new world screw worm); Chrysomya bezziana (old world screw worm) and Wohlfahrtia magnifica (Wohlfahrt’s myiasis fly).

W. magnifica is an obligate parasite of warm-blooded vertebrates in South-eastern Europe, Asiatic Russia, the Near East and North Africa. C. bezziana and C. hominovorax has been recorded attacking sheep and goats (as well as cattle, horses, pigs and dogs). Lesion foci are usually localized on the scalp, face, forearms and on the chest. Insects deposit eggs on the skin, they in turn, penetrate beneath the skin tissue where larvae mature.

61. A  married couple  consulted  a specialist at the genetic consultation about probability of having children  with hemophilia. Both spouses are healthy,  but the  wife’s father  has  hemophilia. In  this family hemophilia may be passed to:

Explanation

Hemophilia is a group of sex-linked inherited blood disorders characterized by prolonged clotting time. However, the bleeding time is normal. Usually, it affects the males, with the females being the carriers. Hemophilia occurs due to lack of formation of prothrombin activator. That is why the coagulation time is prolonged. The formation of prothrombin activator is affected due to the deficiency of factors VIII, IX or XI.

   Types of hemophilia: 

*Hemophilia A or classic hemophilia - deficiency of factor VIII (X-LINKED RECESSIVE)

*Hemophilia B or Christmas disease - deficiency of factor IX (X-LINKED RECESSIVE)

*Hemophilia C or factor XI deficiency (AUTOSOMAL RECESSIVE)

It will be passed to the sons – the mother is the carrier.

62. In  the  perianal  folds  of a 5-year-old girl her mother has found some white \"worms\" that caused  itch  and  anxiety  in the  child.  The  \\\\\\\"worms\\\\\\\" were sent  to  the laboratory. During examination the physician saw white filiform helminths 0,5-1 cm long, with pointed ends,  some  helminths had twisted ends. What  is the most likely diagnosis?

Explanation

Enterobius vermicularis causes pinworm infection (enterobiasis). The life cycle is confined to humans. The infection is acquired by ingesting the worm eggs. Perianal pruritus is the most prominent symptom. Pruritus is thought to be an allergic reaction to the presence of either the adult female or the eggs. Scratching predisposes to secondary bacterial infection. In Laboratory diagnosis, the eggs are recovered from perianal skin by using the scotch tape technique and can be observed microscopically. Unlike those of other intestinal nematodes, these eggs are not found in the stools. There are no means of prevention. It is treated with mebendazole.

63.

A woman  delivered  a dead  child with multiple  developmental defects.  What protozoan disease  might have caused  the intrauterine death?

Explanation

ToRCHeS infections: Toxoplasma gondii; Rubella; Cytomegalovirus; HIV; Herpes simplex virus-2; Syphilis. These are microbes that may pass from mother to fetus. Transmission is transplacental in most cases or via delivery. Toxoplasma gondii causes toxoplasmosis. It is transmitted from cat faeces or ingestion of undercooked meat. Congenital infection of the fetus occurs only when the mother is infected during pregnancy. Congenital infection can result in abortion, stillbirth or neonatal disease with encephalitis, chorioretinitis and hepatosplenomegaly.

64. You   are   studying   functioning   of a  bacteria  operon.  The   operator  gene has   been   released  from   the   repressor gene.  Immediately after  this the  following process will start in the cell:

Explanation

Prokaryotic operons contain an operator – a segment of DNA that regulates the activity of the structural genes of the operon. If the operator is not bound by a repressor molecule, RNA polymerase passes over the operator and reaches the protein-coding genes which it transcribes to mRNA. If a repressor molecule is bound to the operator, the polymerase is blocked and does not produce mRNA. As long as the repressor is bound to the operator, no transcription and therefore no proteins are made. However, when an inducer molecule is present, it binds to the repressor, causing the repressor to change shape so that it no longer binds the operator. When this happens, the RNA polymerase can proceed with transcription.

65.

A married couple came to the genetic counselingThe husband suffers from the insulin-dependent diabetes, the wife is healthy.  What  is thprobability that  this couple will have an insulin-dependent child?

Explanation

66.

While on holiday  in the  countryside a  boy  found  a  spider  with  the  following  morphological  peculiarities: body length   of  2  cm,  round   black  abdomen with  two  rows  of red  dots  on  its dorsal surface,  four pairs of segmented extremities covered with tiny black hairs. Identify this arthropod:

 

Explanation

Karakurt spider: the word kara meaning “black” and kurt meaning “worm” comes from the Turkic languages. It is black in colour and is identified by the thirteen (13) spots which are found on its dorsal abdomen. These spots are usually red in colour, but may also be yellow, or orange. The female has a body length of 1 – 2cm (10-20mm), while the male is smaller and reaches 0.5 – 0.8cm (5-8mm) at best. Only the female spider’s bite is dangerous (either for humans or cattle) as the male cannot penetrate the relatively thick epidermis.

67.

A   man   has   worked   in  an   African  country  for  3 years.  A  month  after his   return   to   Ukraine   he   consulted an    ophthalmologist    and    complained about  eye ache,  eyelid  edema,  lacrimation and temporary visual impairment. Underneath   the    eye   conjunctiva   the doctor  revealed  helminths  30-50 mm long with elongated filiform body. What diagnosis might be suspected?

Explanation

Loa Loa filariasis also known as loiasis or African eyeworm. Humans are infected by the bite of the deer fly (mango fly), chrysops, which deposits infective larvae on the skin. The larvae enter the wound, wander in the body and develop into adults. The females release microfilariae that enter the blood, particularly during the day. There is no inflammatory response to the microfilariae or adults, but a hypersensitivity reaction causes transient, localized, nonerythematous, subcutaneous edema (calabar swellings). The most dramatic finding is an adult worm crawling across the conjunctiva of the eye, a harmless but disconcerting event. The disease is found only in tropical central and west Africa, the habitat of the vector Chrysops.

68.

It   was  proved   that   a  molecule   of immature mRNA (precursor mRNA) contained more  triplets  than  amino  acids   found in   the   synthesized  protein. The  reason  for  that  is that  translation is normally preceded by:

Explanation

RNA molecules produced during transcription are functionally inactive. That is why they should undergo certain chemical modifications called processing or post-transcriptional modification of RNA. For eukaryotic mRNA processing includes 3 kinds of such alterations: 5’-capping; 3’-polyadenylation and splicing. Maturation of eukaryotic mRNA usually involves the removal of RNA sequences, which do not code for protein (introns, or intervening sequences) from the primary transcript. The remaining coding sequences, the exons, are joined together to form the mature mRNA. The process of removing introns and joining exons is called splicing. Abnormal splicing variants are implicated in oncogenesis and many genetic disorders (e.g. β-thalassemia).
69.

The  territory of an old burial  ground for animal refuse that hasn’t been used for over 50 years is meant  for house building. But soil investigation showed the presence of viable spores of a causative agent causing  a  very  dangerous disease.  What  microorganism might  have  been  preserved in soil for such a long period  of time?

Explanation

There are two medically important Bacillus species: Bacillus anthracis and Bacillus cereus. Bacillus anthracis causes anthrax. Human disease occurs in 3 main forms: cutaneous, pulmonary (inhalation) and gastrointestinal. Humans are most often infected cutaneously at the time of trauma to the skin, which allows the spores on animal products such as hides, bristles and wool to enter. Spores can also be inhaled or when contaminated meat is ingested. After being inhaled, the organism moves rapidly to the mediastinal lymph nodes and causes hemorrhagic mediastinitis. Pathogenesis is based on the production of two exotoxins  (Anthrax toxin) – edema factor and lethal factor. Hemorrhagic mediastinitis, septic shock hemorrhagic meningitis and death are severe life-threatening complications. In fatal cases, the organism may affect the spleen, liver, intestines, kidneys, adrenal glands and meninges.

70.

Examination   of   a   12   year    old boy with developmental lag revealed achondroplasia: disproportional constitution  with  evident  shortening of  upper and lower limbs as a result of growth disorder of epiphyseal cartilages  of long tubal bones. This disease is:

Explanation

Autosomal dominant: often due to defects in structural genes. Many generations, both male and female are affected. Found in every generation; no generation is left out (skipped). Parent – child in every generation.

Autosomal recessive is usually seen in some generations (other generations are skipped).

It is sex linked, if only males or only females(X-linked) are affected.

           X-linked dominant: it can be transmitted through both parents. Mothers transmit to 50% of daughters and sons; fathers transmit to all daughters but no son (father-daughters; no generation is left out).

X-linked recessive: sons of heterozygous mothers have a 50% chance of being affected. No male-to-male transmission. Recessive genetic diseases skips generations.

Y-linked: father to all sons; no female involvement (mother or daughter)

71.

A boy has I (I 0I0 ) blood  group  and his sister has IV (I A IB  ) blood group. What blood groups do their parents have?

Explanation

          IAIO                            IBIO

     IAIB   IAIO              IBIO        IOIO

This is the only combination that can produce a group I (IOIO) and a group IV (IAIB) blood groups.

72. Hartnup disease is caused by point mutation of only one gene which results in  disturbance  of  tryptophane  absorption in the bowels and its resorption in the renal tubules.  It is the reason  for disorder of both  digestive  and  urination systems. What genetic phenomenon is observed  in this case?

Explanation

* Pleiotropy: one gene defect contributes to multiple phenotypic effects → disorder of connective tissue and eye lens structure, abnormalities of CNS, arachnodactylia. Marfan is FBN1 gene mutation on chromosome 15; Marfan and Hartnup is one gene defect causing multiple phenotypic defects; likewise Hartnup disease (digestive and Urinary systems)

73.

According to the data of WHO, for about 250 mln of Earth population fall ill with malaria. This disease is mostly spread in tropical and subtropical regions. Range of its spread falls into the areal of the following mosquitoes:

Explanation

74. In some regions of South Africa there is a spread sickle-shaped cell anemia, in which erythrocytes have shape of a sickle as a result of substitution of glutamin by valine in the hemoglobin molecule. What is the cause of this disease?

Explanation

Sickle cell hemoglobin (HbS) point mutation causes a single amino acid replacement in β chain of hemoglobin (substitution of glutamic acid with valine). Pathogenesis of sickle cell anemia: low O2, high altitude or acidosis precipitates sickling – modified shape (deoxygenated HbS polymerizes) → anemia and vaso-occlusive disease. Clinical findings include: dizziness, general weakness, fatigue, “crew-cut” on skull X-ray due to marrow expansion from increased erythropoiesis (this is also seen in thalassemia)  etc. Sickle cells are crescent-shaped RBCs.

75.

A 32 y.o. man is tall, he has gynecomastia, adult woman pattern of hair distribution, high voice, mental deficiency, sterility. Provisional diagnosis is Klinefelter’s syndrome. In order to specify diagnosis it is necessary to analyze:

Explanation

Barr body is an inactive X-chromosome. So a boy (XY) with an inactive X-chromosome must have an additional X-chromosome – XXY (Klinefelter’s syndrome). Causes :

* nondisjunction (maternal and paternal nondisjunction in meiosis I)

* Mosaicism: with the karyotype being 46, XY/47, XXY

Manifestations: gynecomastia, female pattern of pubic hair distribution, no facial hair, high voice.

Diagnosis of most numerical chromosomal disorders (down, patau, edward, klinefelter, turner\'s) can be carried out using the Karyotype.

76.

Autopsy of a newborn boy revealed polydactylia, microcephalia, cheiloschisis and uranoschisis as well as hypertrophy of parenchymatous organs. These defects correspond with the description of Patau’s syndrome. What is the most probable cause of this pathology?

Explanation

Trisomy 13 (Patau’s syndrome): the main abnormalities of this syndrome are mental retardation, holoprosencephaly, congenital heart defects, microcephaly, polydactylyl, microphthalmus, anophthalmos, cleft lip and palate (cheiloschisis and uranoschisis respectively).

77. The first grade pupils were examined in order to sort out children for tuberculosis revaccination. What test was applied for this purpose?

Explanation

Tuberculin (Mantoux) skin test: this test is done by intradermal injection of tuberculoprotein (tuberculin), purified protein derivative (PPD). Type IV hypersensitivity reaction.

The Mantoux skin test should be read between 48 and 72hrs after administration. The basis of reading  is the presence or absence of induration, which may be determined by inspection and by palpation. A record should also be made of formation of vesicles, bullae, lymphangitis, ulceration and necrosis at the test site. The formation of vesicles, bullae or necrosis at the test site indicates positive result. A negative mantoux result usually signifies that the individual has never been exposed to Mycobacterium tuberculosis i.e. absence of cell mediated immunity to tuberculin.

78.

A patient has symptoms of inflammation of urogenital tracts. Examination of a vaginal smear revealed big monocellular, pear-shaped organisms with the pointed spike at the posterior end of body, big nucleus and undulating membrane. What protozoa were found in the smear?

Explanation

In the urogenital tract, the flagellate protozoa, Trichomonas vaginalis is the important pathogen. Trichomonas vaginalis causes trichomoniasis. It is a pear-shaped organism with a central nucleus and four anterior flagella. It has an undulating membrane that extends about two-thirds of its length. It exists only as a trophozoite; there is no cyst form. The organism is transmitted by sexual contact and the primary locations of the organism are the vagina and the prostate. In women, a watery, foul-smelling, greenish vaginal discharge accompanied by itching and burning occurs.

79.

A patient complains of pain in the area of his liver. Duodenal intubation revealed yellowish, oval, narrowed at the poles eggs with an operculum at the end. Size of these eggs is the smallest among all helminth eggs. What is the most probable diagnosis?

Explanation

80. In course of practical training students studied a stained blood smear of a mouse with bacteria phagocyted by leukocytes. What cell organella completes digestion of these bacteria?

Explanation

Lysosomes are small organelles containing digestive enzymes, their derivatives include phagosomes, phagolysosomes, autophagosomes and autophagolysosomes. Lysosomes are digestive organelles rich in hydrolytic enzymes such as proteases, nucleases, glucosidases, lipases and phospholipases. 3 pathways for digestion exist:

·        Extracellular large particles such as bacteria, cell debris and other foreign materials are engulfed in the process of phagocytosis. A phagosome, formed as the material is internalized within the cytoplasm, subsequently fuses with a lysosome to create a phagolysosome.

·        Extracellular small particles such as extracellular proteins, plasma membrane proteins and ligand-receptor complexes are internalized by endocytosis and receptor mediated endocytosis.

·        Intracellular particles such as entire organelles, cytoplasmic proteins and other cellular components – autophagy.

81.

Slime, blood and protozoa 30-200 microns long have been revealed in a man’s feces. The body is covered with cilias and has correct oval form with a little bit narrowed anterior and wide round shaped posterior end. At the anterior end a mouth is visible. In cytoplasm there are two nuclei and two short vacuoles. What are the described features typical for?

Explanation

        Balantidium coli cause balantidiasis. It is the only ciliated protozoan that causes human disease i.e. diarrhea. Domestic animals, especially pigs are the main reservoir for the organism and humans are infected after ingesting the cysts in food or water contaminated with animal or human faeces. Diagnosis is made by finding large ciliated trophozoites or large cysts with a characteristic V-shaped nucleus in the stool. The trophozoites excyst in the small intestine, travel to the colon (large intestine) and by burrowing into the wall cause an ulcer similar to that of Entamoeba histolytica.

82. A man who was bitten by the unknown dog applied to the surgeon. Wide ragged wounds were localized on the face. What curative-prophylactic aid should be given to prevent rabies?

Explanation

As the name implies, anti-rabies vaccine is used to prevent (prophylaxis) rabies. It can also be used for treatment (curative). Rabies is a viral disease of animals and humans can be infected by animal’s bite (most common – Dog). A dog can be immunized against the disease.
83.

A sick man with high temperature and a lot of tiny wounds on the body has been admitted to the hospital. Lice have been found in the folds of his clothing. What disease can be suspected?

Explanation

Epidemic typhus (human body louse) – Rickettsia prowazekii, can remain latent and reactivate months or years in an infected patient, with symptoms similar to or even identical to the original attack of typhus, including a rash that starts centrally and spreads out, sparing palms and soles. This delayed relapse of epidemic typhus – Brill’s disease.

Epidemic typhus - Lice

84.

A patient with suspicion on epidemic typhus was admitted to the hospital. Some arachnids and insects have been found in his flat. Which of them may be a carrier of the pathogen of epidemic typhus?

Explanation

Epidemic typhus (human body louse) – Rickettsia prowazekii, can remain latent and reactivate months or years in an infected patient, with symptoms similar to or even identical to the original attack of typhus, including a rash that starts centrally and spreads out, sparing palms and soles. This delayed relapse of epidemic typhus – Brill’s disease.

Epidemic typhus - Lice

85. A businessman came to India from South America. On examination the physician found that the patient was suffering from sleeping-sickness. What was the way of invasion?

Explanation

     The genus Trypanosoma includes 3 major pathogens: Trypanosoma cruzi, Trypanosoma gambiense and Trypanosoma rhodesiense. T. cruzi causes American trypanosomiasis (chagas disease); the reduvid bug (kissing bug or Triatoma) is the vector.

T. gambiense and T. rhodesiense cause sleeping sickness (African trypanosomiasis); the vector for both is the tse-tse fly (Glossina).

86. Hypertrychosis of auricles is caused by a gene that is localized in Y-chromosome. Father has this feature. What is the probability to give birth to a boy with such anomaly?

Explanation

Every male child has the Y-chromosome. A Y-linked disease only affects males and a diseased father will pass it to all (100%) his male children. Male sex chromosome (XY)

87.

A tissue sample of benign tumor was studied under the electron microscope. A lot of small (15-20 nm) spherical bodies, consisting of 2 unequal subunits were detected. These are:

Explanation

A large number of components are required for translation (synthesis of a protein). These include all the amino acids that are found in the finished product, the mRNA to be translated, tRNA, functional ribosomes, energy sources and enzymes as well as protein factors needed for initiation, elongation and termination of the polypeptide chain. In eukaryotic cells, the ribosomes are either “free” in the cytosol or are in close association with the endoplasmic reticulum (which is then known as the “rough” endoplasmic reticulum or RER). The RER – associated ribosomes are responsible for synthesizing proteins that are to be exported from the cell as well as those that are destined to become integrated into plasma, endoplasmic reticulum or golgi membranes or incorporated into lysosomes.

88.

Parents with an ill child consulted an infectionist. They had been working in one of Asian countries for a long time. The child has sallow skin, loss of appetite, laxity, enlarged liver, spleen, peripheral lymph nodes. What protozoal illness can be suspected?

Explanation

The genus Leishmania includes 4 major pathogens: Leishmania donovani; L. tropica; L. Mexicana and L. braziliensis. Leishmania donovani is the cause of kala-azar (visceral leishmaniasis). In visceral leishmaniasis, the organs of the reticuloendothelial system (liver, spleen and bone marrow) are the most severely affected. It occurs in the Middle East, southern Russia, China, India and Sub-saharan Africa. The lifecycle involves the sandfly as the vector and a variety of mammals such as dogs, foxes and rodents as reservoirs.

89.

Healthy parents have got a fair-haired, blue-eyed girl. Irritability, anxiety, sleep and feeding disturbance developed in the first months of the infant’s life. Neurological examination revealed developmental lag. What method of genetic investigation should be used for the exact diagnosis?

Explanation

90.

Part of the DNA chain turned 180 degree as a result of gamma radiation. What type of mutation took place in the DNA chain?

Explanation

Inversion involve an end-to-end reversal of a segment within a chromosome e.g. ABCDEF becomes ABFEDC  1800.

91. Analysis of amniotic fluid that was obtained as a result of amniocentesis (puncture of amniotic sac) revealed cells the nuclei of which contain sex chromatin (Barr’s body). What can it be evidence of?

Explanation

Barr body is an inactive X-chromosome. A normal female has one barr body XX; so in turner’s syndrome, there is no barr body because the only X present is the active one (45 XO); likewise in a normal male fetus XY
92.

A woman with 0 (I) blood group has born a child with AB blood group. This woman’s husband has A blood group. What genetic interaction explains this phenomenon?

Explanation