4. Nail-patella syndrome in humans is characterized by congenital abnormalities

Question

4. Nail-patella syndrome in humans is characterized by congenital abnormalities of the fingernails (and sometimes toenails) and the patellae (kneecaps). The gene for this disorder
BIOL 321 | Problem Set 3
is dominant and is located on chromosome 9 about 10 map units from the ABO locus. Suppose a man with nail-patella syndrome and type A blood marries a normal woman with type B blood. The mothers of both the husband and the wife are normal and have type O blood.

a) The husband and the wife have two children, one with type A blood and the other with type B. What is the probability that both children have normal fingernails and patellae?
b) The couple are now expecting another child. What is the chance that the child will have nail-patella syndrome and type O blood?
c) Amniocentesis reveals that the fetus has type AB blood. What is the chance that it has nail-patella syndrome?

Explanation / Answer

Nail-patella syndrome is known to be linked with ABO locus from different studies.

mother with B and father with A blood group: child can be A/B/AB/O. the syndrom is dominant (3:1 chances). having both the child for the syndrme is 75%

B) the 3rd child for having the syndrome is 50%

cances of AB blood type is 25% so 25% with the syndrome

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