A man has six fingers on each hand and six toes on each foot His wife and their daughter have the normal number of digits What fraction of this couple's children would be expected to have extra digits?

Answer 1

If the trait is autosomal recessive the odds that he'll have children with six digits would be zero unless his wife was heterzygous for the trait. Then, the odds would be a 50% chance that the trait would occur in each of their offspring.

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Because the daughter is normal the man's genotype must be heterozygous for the trait so:

if X = extra digits and x = normal (5) digits then:

50% of the offspring will be polydactylic