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Question 1
Incorrect
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All are true about monozygotic pregnancy, EXCEPT:
Your Answer: There is only one placenta
Correct Answer: The 1st commonly presents as breech
Explanation:The 1st commonly presents as cephalic. 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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Question 2
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 3
Incorrect
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Which of the following statements regarding BRCA gene mutations is true?
Your Answer: Around 1 in 10 people diagnosed with breast cancer will have either the BRCA 1 or BRCA 2 gene 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 4
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: 30%
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 5
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 6
Incorrect
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Regarding Turner syndrome which of the following statements is true?
Your Answer: Turner syndrome occurs in approximately 1 in every 20,000 live female births
Correct 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 7
Incorrect
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Regarding monozygotic twins, all of the following are correct, EXCEPT:
Your Answer: Constitutes 1/3 of twins
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 8
Incorrect
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Question 9
Incorrect
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A pregnant patient who is needle phobic has her nuchal translucency (NT) scan but refuses serum markers. You advise her the False Positive Rate of the scan is 5%. What would you advise the mother regarding the detection rate of Down Syndrome using NT alone?
Your Answer: 40%
Correct Answer: 70%
Explanation:The nuchal lucency measurement is the measure of the nuchal pad thickness. Children with down syndrome have an increased thickness of the nuchal pad. The risk of down’s syndrome increases with maternal age. The nuchal lucency test has an accuracy rate of 70%.
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This question is part of the following fields:
- Genetics
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Question 10
Correct
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You see a patient in fertility clinic who you suspect has Klinefelters. What is the likely karyotype?
Your Answer: 47XXY
Explanation:Klinefelter syndrome occurs in 1:1000 individuals. They are phenotypically male and genotypically they have 47,XXY chromosomes. These individuals have small testes, are tall with disproportionate long lower limbs.40% will also have gynecomastia.
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This question is part of the following fields:
- Genetics
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