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Flashcards in Genetics Deck (14)
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1

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

2

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

3

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

4

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

5

Klinefelters syndrome characteristics include all of the following except:
A - testicular hypoplasia
B - low testosterone
C - azoospermia
D - impotence

D - impotence

6

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

7

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%

8

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

9

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

10

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

11

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

12

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.

13

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

14

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