Genetics Flashcards
A woman’s previous son has Duchene muscular dystrophy. What is the chance that her current fetus is affected? a - 0% b - 10% c - 25% d - 33% e - 50%
c - 25%
X-linked recessive
What percentage of patients are negative for HpA1a antigen?
A - 0.0002% B - 0.02% C - 0.2% D - 2% E - 20%
D - 2%
Majority of people are HPA 1a for platelats
A man has an X-linked disorder and his wife is homozygous normal. What is the chance that their two children will both be affected? a - 0 b - 1/2 c - 1/4 d - 1/16 e - 1/32
a - 0
0% if x-linked recessive
50% if x-linked dominant for each baby
- therefore 25% that both will be affected
All of the following patterns of inheritance are correct except:
A - von Recklinghausen’s – autosomal dominant
B - Huntington’s chorea – autosomal dominant
C- Cystic fibrosis – autosomal recessive
D - Tay Sach’s – autosomal dominant
D - Tay Sach’s – autosomal dominant
Autosomal recessive
von Recklinghausen’s – autosomal dominant, neurofibromatosis type 1
Klinefelters syndrome characteristics include all of the following except: A - testicular hypoplasia B - low testosterone C - azoospermia D - impotence
D - impotence
The husband of a normal female has Christmas disease. She gave birth to a son. What is the probability that he is affected? A - none B - 10% C - 25% D - 33% E - 50%
A - none
An adopted woman has recently been informed that her natural mother died from Huntington’s chorea. What is the risk that her unborn child is affected? A - 50% B - 25% C - none D - none if the baby is male E - none if the baby is female
B - 25%
Which of the following conditions is autosomal recessive? A - haemophilia A B - cystic fibrosis C - tuberous sclerosis D - Huntington’s chorea E - adult polycystic kidney disease
B - cystic fibrosis
tuberous sclerosis - rare, autosomal dominant, benign tumours in kidneys, liver, heart, lung, eyes
Which of the following tests is most useful in diagnosing haemoglobinopathy?
A - HbEPG B - Bone marrow C - DNA analysis D - Red cell index E - Blood film
A - HbEPG
HbEPG - haemboglobin electrophoresis, this checks for HbS carrier status, thalassaemia
Suction curettage for missed abortion at 10/40. What size suction catheter should you use? A - 6 B - 8 C - 10 D - 12 E - 14
C - 10
One partner of a couple with recurrent miscarriage has a balanced reciprocal translocation – the most correct is:
A - phenotypically normal offspring in 50% of conceptions
B - major anomalies with trisomy in 25%
phenotypically normal in 10% if husband has translocation
C - phenotypically normal in 70% if mother has translocation
D - all offspring will have a balanced translocation
A - phenotypically normal offspring in 50% of conceptions
Fragile X syndrome
A - occurs only in men B - Mendelian inheritance C - associated with premature menopause D - no phenotypic features E - none of the above
C - associated with premature menopause
Fragile X syndrome has traditionally been considered an X-linked recessive condition with variable expressivity and possibly reduced penetrance. However, due to genetic anticipation and X-inactivation in females, the inheritance of Fragile X syndrome does not follow the usual pattern of X-linked dominant inheritance, and some scholars have suggested discontinuing labeling X-linked disorders as dominant or recessive. Females with full FMR1 mutations may have a milder phenotype than males due to variability in X-inactivation.
Which chromosomal abnormality doesn’t increase in frequency with increased maternal age?
A - trisomy 21
B - trisomy 18
C - Turners XO
D - XXY
C - Turners XO
Klinefelters – advice to pregnant woman about likely phenotype. Which is not a feature?
A- gynaecomastia B - female fat distribution C - serious mental retardation D- infertility E - tall eunuchoid habitus
C - serious mental retardation
only mild intellectual disability
