Genetic Studies of an Animal Show That Eye Color Is

Genetic studies of an animal show that eye color is controlled by an autosomal gene with the dominant allele ( R ) for red eye color and the recessive allele ( r ) for yellow eye color. A second autosomal gene has the dominant allele ( T ) for paws with thumbs and the recessive allele ( t ) for paws without thumbs. The genetic cross RRTT x rrtt creates offspring with genotype RrTt . One of those dihybrids is mated in a testcross ( RrTt x rrtt ) . If the two genes are completely linked (no recombination occurs between them) , then the testcross should produce offspring with the phenotype ratio ____.

A) three red-eyed with thumbs: one yellow-eyed without thumbs
B) one red-eyed with thumbs: one yellow-eyed with thumbs: one red-eyed without thumbs: one yellow-eyed without thumbs
C) one red-eyed with thumbs: one yellow-eyed without thumbs
D) nine red-eyed with thumbs: three yellow-eyed with thumbs: three red-eyed without thumbs: one yellow-eyed without thumbs
E) one yellow-eyed with thumbs: one red-eyed without thumbs