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Question 1
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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Question 2
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 3
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 4
Correct
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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: 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
Incorrect
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A 40 year old women who is 13 weeks pregnant is found to have be high risk for Downs following the combined screening test. What is the most appropriate further test to see if the foetus is affected?
Your Answer: Nuchal thickness imaging
Correct Answer: Chorionic Villous Sampling
Explanation:Chorion villus sampling is an invasive procedure which aims to collect the rapidly dividing cells in the placenta. It is used for numerous reasons including detection of early pregnancy, viability of the foetus, singleton pregnancy, confirm gestation age and for prenatal diagnosis of the fetal chromosomal abnormalities including diagnosis of Down’s syndrome. However it hold a 2% chance of miscarriage during the procedure. Nuchal thickness and imaging are part of the combined test that must have been performed before.
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This question is part of the following fields:
- Genetics
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Question 6
Correct
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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: 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 7
Correct
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Which of the following is the leading cause of Down Syndrome?
Your 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 8
Correct
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Question 9
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 10
Correct
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Regarding twin pregnancies all of the following are correct EXCEPT:
Your 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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