A man has extra digits (six fingers on each hand and six toes on each foot). His wife and their daughter have the normal number
of digits (five fingers on each hand and five toes on each foot.) The couple's second child has extra digits. What is the probability that their next (third) child will have extra digits?a. 9/16. b. 3/4.
c. 1/16.
d. 1/2.
e. 1/8.
Extra digits on hands and feet mean an individual has six fingers in each hand and feet, this is known as polydactyly. Polydactyly shows an autosomal dominant type of inheritance pattern.
In this case, the mother is normal so she must be recessive alleles and the first daughter is normal so the father must have a recessive allele which means he is heterozygous.
Cross:
Man = Dd
Woman = dd
Their children :
D d
d Dd dd
d Dd dd
Probability of polydactyl child = 2/4 or 1/2 or 50%
