Answer: The genotype ratio of their children is 2Ff : 2 ff
The phenotype ratio is 2 polydactyl individuals : 2 normal individuals.
Explanation: Let F represent the gene for extra finger while f represent the gene for normal finger. From the information provided, F is dominant while f is recessive. A heterozygous parent will have a genotype of Ff while a normal parent will have a genotype of ff. A cross between them will produce 2 Ff and 2 ff. Ff will manifest phenotypically as polydactyl because F is a dominant allele while ff will manifest phenotypically as normal fingers because f is recessive. For a recessive allele to express itself outwardly, it must occur in a homozygous state. Ff is heterozygous polydactyl.
See the attached punnet square for more information
