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Question 1
Incorrect
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Which of the following is the leading cause of Down Syndrome?
Your Answer: Robertsonian Translocation
Correct Answer: Nondisjunction maternal gamete
Explanation:Most of the cases of down syndrome occur due to non disjunction trisomy 21 which is associated with increased maternal age. The non disjunction occurs in the maternal gametes.
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This question is part of the following fields:
- Genetics
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Question 2
Correct
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A woman has undergone genetic testing due to her family history and has the BRCA 1 gene. What would you advise her lifetime risk of ovarian cancer is?
Your Answer: 40%
Explanation:The most common hereditary cancer in the breast ovarian cancer syndrome accounts for 90% of the hereditary cancers. It is due to mutations in the BRCA 1 and BRCA 2 genes, most commonly the BRCA 1 gene accounting for 70% life time risk of breast cancer and 40% life time risk of ovarian cancer.
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This question is part of the following fields:
- Genetics
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Question 3
Incorrect
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Regarding monozygotic twins, all of the following are correct, EXCEPT:
Your Answer: Has a constant incidence of 1:250 births
Correct Answer: Has a constant incidence 1:600 births
Explanation:The incidence of monozygotic twins is constant worldwide (approximately 4 per 1000 births). Approximately two thirds of twins are dizygotic.
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This question is part of the following fields:
- Genetics
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Question 4
Correct
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The following are true for dizygotic twins EXCEPT:
Your Answer: Both twins are identical & of the same sex
Explanation:Dizygotic means two (di) fertilized eggs (zygotes). Dizygotic twins occur when two eggs are fertilized by two separate sperm. Dizygotic twins are also known as fraternal or non-identical twins. They are the most common type of twins.
Unlike monozygotic twins (also known as identical twins), dizygotic twins do not share the same genes. Monozygotic twins share 100 percent of each other genes. Dizygotic twins share only 50 percent. This is the same genetic similarity found between siblings conceived and born at different times.
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This question is part of the following fields:
- Genetics
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Question 5
Correct
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You are called to assist in an initially midwife led delivery. Upon delivering a female baby you notice the baby has partial fusion of the labioscrotal folds. You suspect congenital adrenal hyperplasia. Which of the following genes is most likely to be mutated?
Your Answer: CYP21A
Explanation:CAH leads to virilization of the female foetus. It occurs to an enzyme deficiency (21-hydroxylase). This results in a reduced levels of corticosteroids from being circulated resulting in hyperplasia of the adrenal glands and increased progesterone production. The CYP21A gene has been implicated in causes this deficiency.
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This question is part of the following fields:
- Genetics
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Question 6
Incorrect
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Which of the following statements regarding BRCA gene mutations is true?
Your Answer: 15% of people diagnosed with breast cancer will have a BRCA1 or BRCA 2 mutation
Correct Answer: They account for around 25% of inherited breast cancers
Explanation:Hereditary breast cancers account for 10 % of the cases. BRCA gene mutations account for 25 % of these cancers.
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This question is part of the following fields:
- Genetics
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Question 7
Correct
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Regarding Turner syndrome which of the following statements is true?
Your Answer: Only 1% of affected foetuses will survive to term
Explanation:The incidence of 45,XO turner syndrome is around 1 in 8000 live births. Approximately 1% of monosomy X female embryos survive. Phenotypically they are females and 90% do not develop secondary sexual characteristics and hormone replacement is required.
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This question is part of the following fields:
- Genetics
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Question 8
Incorrect
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A women has undergone genetic testing due to her family history and has the BRCA 1 gene. What would you advise her lifetime risk of breast cancer is?
Your Answer: 15%
Correct Answer: 70%
Explanation:The life time risk of breast cancer in BRCA 1 gene is 70% and of ovarian cancer is 40%.
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This question is part of the following fields:
- Genetics
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Question 9
Correct
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If both parents have beta-thalassaemia minor, what is the chance of their male offspring having beta thalassemia major?
Your Answer: 25%
Explanation:This is not an X-linked condition so the sex of the child makes no difference to the inheritance. Any child will have a 1 in 4 chance of having beta thalassaemia major.
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This question is part of the following fields:
- Genetics
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Question 10
Incorrect
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Regarding twin pregnancies all of the following are correct EXCEPT:
Your Answer: It has a higher incidence of preterm labour
Correct Answer: Identical or monozygotic twins arise from fertilization of two ovum
Explanation:Monozygotic (MZ) twins originate when a single egg is fertilized to form one zygote, which then divides into two embryos. Although they share the same genotype they are not phenotypically identical.
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This question is part of the following fields:
- Genetics
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