Genetics

Question 1

1. Regarding teratogens in pregnancy, which statement is correct?
2. the use of anticonvulsants in pregnancy is generally not associated with an increased risk of congenital malformations
3. a safe period for alcohol exposure in pregnancy has been established.
4. retinoid use in pregnancy may be safe
5. risks of fetal malformation in a diabetic mother remain elevated despite good control
6. human teratogens affect all genetic backgrounds with the same severity

Answer 1

4. risks of fetal malformation in a diabetic mother remain elevated despite good control

Question 2

2. Which of the following diagnostic techniques is of no value for the diagnosis of neural tube defects?
3. Amniocentesis
4. Chorion villus sampling (CVS)
5. Maternal serum screening
6. Ultrasonography

Answer 2

2. Chorion villus sampling (CVS)

Question 3

3. A baby born with pulmonary hypoplasia secondary to oligohydramnios caused by renal agenesis would be classified as having:
4. an association.
5. a dysplasia.
6. a sequence.
7. a syndrome.

Answer 3

3. a sequence.

Question 4

4. The most common chromosome abnormality in first trimester spontaneous miscarriages is:
5. trisomy
6. monosomy
7. triploidy
8. tetrasomy

Answer 4

1. trisomy

Question 5

5. Which of the following karyotypes is diagnostic of Down syndrome
6. 46,XX,der(14;21)(q10;q10)pat+21
7. 47,XY,+13
8. 45,XX,rob,(14;21)(q10;q10)
9. 46,XY,t(2;3)(q21;q12)

Answer 5

1. 46,XX,der(14;21)(q10;q10)pat+21

Question 6

6. In a Robertsonian translocation fusion occurs at the:
7. telomeres
8. centromeres
9. histones
10. ends of the long arms

Answer 6

2. centromeres

Question 7

7. The presence of two or more cell lines from different zygotes in a single individual is known as:
8. mosaicism.
9. diploidy.
10. aneuploidy.
11. chimaerism.

Answer 7

4. chimaerism.

Question 8

8. Which of the following trisomy karyotypes has the mildest effect on human development?
9. 47,XXX
10. 47,XXY
11. 47,XX,+13
12. 47,XY,+21

Answer 8

1. 47,XXX

Question 9

9. A child with hypoplastic left heart syndrome is being evaluated prior to consideration of a heart transplant. Which of the following karyotypes is most likely to be found on chromosomal analysis?
10. 45,X
11. 46,XX
12. 46,XX,del(22)(q11.2q11.2)
13. 46,XY.ish del(7)(q11.23q11.23)(ELN-)
14. 47,XXY

Answer 9

2. 46,XX

Question 10

10. You are asked to evaluate a well infant girl with apparently isolated Pierre Robin sequence. Which of the following diagnostic tests is most likely to yield a useful clinical finding?
11. Chromosome analysis
12. Electrocardiogram (ECG)
13. Eye exam
14. FISH for del22q11.2
15. Skeletal survey

Answer 10

3. Eye exam

Question 11

11. What is the name of the genetic syndrome characterized by the phenotype shown above?
12. Down syndrome
13. Marfan syndrome
14. William syndrome
15. Smith Lemli Opitz syndrome

Answer 11

3. William syndrome

Question 12

13. Which of the following is not a chromosome instability syndrome?
14. Klinefelter syndrome
15. Ataxia telangiectasia
16. Fanconi anaemia
17. Bloom syndrome

Answer 12

1. Klinefelter syndrome

Question 13

14. A nonsense mutation involves:
15. a regulatory sequence.
16. an AG splice acceptor site.
17. the creation of a different amino acid.
18. the creation of a stop codon.

Answer 13

4. the creation of a stop codon.

Question 14

15. Exon skipping is associated with:
16. nonsense mutations.
17. regulatory mutations.
18. RNA processing mutations.
19. silent mutations.

Answer 14

3. RNA processing mutations.

Question 15

16. Male to male transmission is a key feature of which pattern of inheritance?
17. Autosomal dominant
18. Autosomal recessive
19. X-linked dominant
20. X-linked recessive

Answer 15

1. Autosomal dominant

Question 16

17. Consanguinity shows a strong association with which pattern of inheritance?
18. Autosomal dominant
19. Autosomal recessive
20. X-linked dominant
21. X-linked recessive

Answer 16

2. Autosomal recessive

Question 17

18. Which of the following would be most useful in differentiating non-accidental injury (NAI) from osteogenesis imperfecta in a 5-month-old girl with unexplained fractures?
19. Blue sclerae
20. Healing fractures of different ages
21. Low socioeconomic status of the parents
22. Retinal hemorrhages
23. Type I collagen analysis

Answer 17

4. Retinal hemorrhages

Question 18

I9. If both parents are affected with the same autosomal recessive disorder then the probability that each of their children will be affected equals ___.

1. 1 in 4
2. 1 in 2
3. 2 in 3
4. 1

Answer 18

4. 1

Question 19

20. The most common cystic fibrosis mutation consists of:
21. a deletion
22. a duplication
23. a substitution
24. an insertion

Answer 19

1. a deletion

Question 20

21. The healthy sister of a young man with cystic fibrosis wants to start a family. What is her chance of being a carrier?
22. 5%
23. 25%
24. 33%
25. 50%
26. 67%

Answer 20

5. 67%

Question 21

22. Enzyme assay can be used to identify carriers of:
23. Cystic fibrosis.
24. Fragile X syndrome.
25. Oculocutaneous albinism.
26. Tay-Sachs disease

Answer 21

4. Tay-Sachs disease

Question 22

23. Which of the following is a feature of X-linked dominant inheritance?
24. Parental consanguinity
25. Transmitted by males only to females
26. Transmission only by females
27. Male to male transmission

Answer 22

2. Transmitted by males only to females

Question 23

24. A young girl has been diagnosed as having Duchenne muscular dystrophy. You should check her:
25. Chromosomes
26. Hemoglobin
27. Electrolytes
28. Thyroid function
29. EMG

Answer 23

1. Chromosomes

Question 24

25. A 3-year-old girl has hypodontia, alopecia, and mild developmental delay. Examination reveals hyperpigmented hyperkeratotic streaks. Her sister has severe developmental delay with seizures. Her mother has partial adontia and atrophic scalp hair. Which of the following clinical findings is most commonly associated with this disorder?
26. Affected females can only have unaffected males or affected females.
27. Chromosome analysis of fibroblasts reveal an abnormality in 90% of cases.
28. Germline mosaicism is a common etiology.
29. One sees fewer than expected males in affected families.
30. 67% of cases represent new mutations

Answer 24

4. One sees fewer than expected males in affected families.

Question 25

26. A concerned mother brings her 18-month-old daughter to the pediatrician’s office because she has been intermittently constipated. Her mother became alarmed while changing her diaper straining to have a stool, she found some red, tissue bulging from the rectum. Which of the following procedures or laboratory studies is most like to identify the appropriate diagnosis?
27. Colonoscopy for Crohn disease.
28. Molecular analysis for Duchenne muscular dystrophy
29. Rectal biopsy Hirschsprung disease
30. Renal ultrasound for Beckwith-Wiedemann syndrome
31. Molecular analysis for cystic fibrosis

Answer 25

5. Molecular analysis for cystic fibrosis

Question 26

27. Which feature is NOT suggestive of Fragile-X syndrome?
28. Gaze avoidance
29. Persevered speech
30. Family history of premature ovarian failure
31. Loss of developmental milestones
32. Macrocephaly

Answer 26

4. Loss of developmental milestones

Question 27

28. High blood ammonia level occurs in:
29. galactosaemia.
30. Hurler’s syndrome.
31. ornithine transcarbamylase (OTC) deficiency.
32. phenylketonuria.

Answer 27

3. ornithine transcarbamylase (OTC) deficiency.

Question 28

29. Which of the following conditions is a peroxisomal disorder?
30. Acute intermittent porphyria
31. Maple syrup urine disease
32. Medium chain acyl-CoA dehydrogenase deficiency
33. Zellweger syndrome

Answer 28

4. Zellweger syndrome

Question 29

30. A newborn infant has the Robin sequence. The mother was diagnosed with arthritis in childhood and has had a retinal detachment. Which of the following is the most likely syndromic diagnosis?
31. Acromesomelic dysplasia
32. Rieger syndrome
33. Stickler syndrome
34. Treacher Collins syndrome
35. Warburg syndrome

Answer 29

3. Stickler syndrome

Question 30

31. Radial ray anomalies distinguished by the presence or absence of thumbs can provide a clue toward an appropriate diagnosis. In which of the following syndromes are thumbs consistently present?
32. Thrombocytopenia and absent radius syndrome
33. Fanconi anemia
34. Holt-Oram syndrome
35. VATER association
36. de Lange syndrome

Answer 30

1. Thrombocytopenia and absent radius syndrome

Question 31

32. A child presents to you with congenital abnormalities and cryptorchidism
33. Angelman Syndrome
34. Prader Wili Syndrome
35. Not enough information to be certain

Answer 31

3. Not enough information to be certain

Question 32

33. Prader-Willi syndrome (PWS) can result from either an interstitial deletion involving the paternal copy of chromosome subregion 15q1-q13 or from maternal uniparental disomy of chromosome 15. The reason for this is:
34. The maternal copy of the gene(s) responsible for Angelman syndrome (AS) is imprinted and is not expressed.
35. The maternal copy of the gene(s) responsible for PWS is imprinted and is not expressed.
36. The paternal copy of the gene(s) responsible for PWS is imprinted and is not expressed.
37. The maternal copy of the gene(s) responsible for PWS exerts a dominant negative effect of the paternal allele.
38. PWS results from an anomaly of X-chromosome inactivation.

Answer 32

3. The paternal copy of the gene(s) responsible for PWS is imprinted and is not expressed.

Question 33

34. A child presents with infantile spasms. The top genetic disorder on your differential diagnosis list is:
35. Tuberous sclerosis
36. Neurofibromatosis
37. Rett syndrome
38. Angelman syndrome
39. Tay-Sachs disease

Answer 33

1. Tuberous sclerosis