Consider the Following Genetic Study Involving Two Autosomal Genes

Multiple Choice

Consider the following genetic study involving two autosomal genes. One of these, eye colour, has the dominant allele (R) for red eye colour and the recessive allele (r) for yellow eye colour. The other has the dominant allele (T) leading to paws with thumbs, while the recessive allele (t) codes for paws without thumbs. If these genes are not linked, what should be the phenotype ratio of the offspring produced by a testcross (RrTt × rrtt) ?

A) 1 red-eyed with thumbs : 1 yellow-eyed without thumbs
B) 1 red-eyed with thumbs : 1 yellow-eyed with thumbs : 1 red-eyed without thumbs : 1 yellow-eyed without thumbs
C) 3 red-eyed with thumbs : 1 yellow-eyed without thumbs
D) 9 red-eyed with thumbs : 3 yellow-eyed with thumbs : 3 red-eyed without thumbs : 1 yellow-eyed without thumbs