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 ) . Based on the principle of independent assortment, the testcross should produce offspring with the phenotype ratio ____.

A) 3 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) 1 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
E) 3 yellow-eyed with thumbs : 1 red-eyed without thumbs