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Question 1
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 2
Correct
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All are true about monozygotic pregnancy, EXCEPT:
Your 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 3
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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Question 4
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 5
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 6
Correct
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Which of the following statements regarding BRCA gene mutations is true?
Your 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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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 8
Correct
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Which of the following statements regarding Management of Beta Thalassaemia in Pregnancy is not part of the RCOG guidelines?
Your Answer: Folic acid 5 mg daily should be commenced 12 months prior to conception
Explanation:Women with Beta-Thalassaemia require significant extra input during pregnancy. Folic acid 5 mg daily should be commenced 3 months prior to conception in these patients. NOTE Women with thalassaemia who have undergone splenectomy OR have a platelet count >600 should continue or be commenced on Aspirin (75 mg/day)
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This question is part of the following fields:
- Genetics
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Question 9
Correct
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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: 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 10
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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