Question

In an imaginary mammal, C (red) and c (black) are dominant and recessive alleles of a gene controlling fur color; R (green) and r (brown) are dominant and recessive alleles of a gene controlling eye color. The alleles of these genes assort independently. Provide the correct ratios of phenotypes for each cross:

a) Cc Rr xx cc rr
b) CCRR x ccrr
c) CcRr×CcRr
d) cc RR × CC Rr
e) cc rr × Cc rr
f) CCrr×CCRr

Answer 1

For cross e) cc rr × Cc rr, all offspring will have black fur and brown eyes, resulting in a 100% phenotypic ratio for this combination. For cross f) CC rr × CCRr, all offspring will have red fur with a 1:1 phenotypic ratio of green eyes to brown eyes.

Step-by-step explanation:

The question deals with Mendelian genetics and specifically looks at phenotypic ratios resulting from the crosses between different genotypes of an imaginary mammal. For each cross, we need to consider the independent assortment of alleles and calculate the resulting phenotypes.

e) The cross cc rr × Cc rr results in all offspring having black fur (since c is recessive and there is at least one C allele from the heterozygous parent), and brown eyes (since both parents are homozygous recessive rr). Therefore, the phenotypic ratio for this cross is 100% black fur with brown eyes.

f) The cross CC rr × CC Rr results in all offspring having red fur (due to the presence of two dominant C alleles) and a mix of 50% green eyes and 50% brown eyes (due to the one parent being heterozygous for the eye color gene). Thus, the phenotypic ratio here is 1:1 for green-eyed red fur and brown-eyed red fur offspring.

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