Arlo Guthries father Woody died at the age of 55 of the very

Arlo Guthrie\'s father, Woody, died at the age of 55 of the very rare autosomal dominant trait called Huntington\'s disease. Only 1 person per 10,000 people of Western European descent carry one copy of this allele; homozygotes do not occur. This disease causes gradual deterioration of the nervous system and eventual death. Huntington\'s disease is unusual because symptoms are not expressed until later life in heterozygotes; homozygotes die at an early age before they can reproduce. Woody Guthrie was not affected until he was 40 years old. Arlo\'s mother was normal. What is the probability that Woody’s son Arlo would develop Huntington\'s disease?

Solution

What is the probability that Woody’s son Arlo would develop Huntington\'s disease?

huntington\'s disease-----------dominant allele----H

homozygote-condition (HH) ---------lethal

symptoms are not expressed until later life in heterozygotes\\

Arlo Guthrie\'s father-------- heterozygotes-----------genotype------Hh

Mother –normal genotype------------hh

Father genotype------Hh          x Mother –normal genotype------------hh

H

h

h

Hh heterozygote

hh           normal

h

Hh heterozygote

hh           normal

Answer == 2/4 =1/2==0.50