Question

In mice, the allele for gray fur (G) is dominant to the allele for brown fur (g). The allele (L) for long tail is dominant to the allele (l) for short tail. A cross is made between two mice that are heterozygous for gray and long tail. What is the expected phenotype ratio of the offspring?

Answer 1

The expected phenotypic ratio of offspring from two heterozygous gray fur and long tail mice (GgLl x GgLl) is 9 gray with long tail : 3 gray with short tail : 3 brown with long tail : 1 brown with short tail, following a 9:3:3:1 dihybrid cross pattern.

Step-by-step explanation:

The phenotypic ratio of offspring from two mice that are heterozygous for grey fur (Gg) and long tail (Ll) can be calculated using a Punnett square. Since each parent has the genotype GgLl, the phenotypic ratio follows a dihybrid cross pattern. Each genotype has a 25% chance of occurring, and we group these by phenotype to get the ratio.

• GG LL (Gray, Long Tail)
• GG Ll (Gray, Long or Short Tail)
• Gg LL (Gray, Long Tail)
• Gg Ll (Gray, Long or Short Tail)
• gg LL (Brown, Long Tail)
• gg Ll (Brown, Long or Short Tail)
• Gg ll (Gray, Short Tail)
• gg ll (Brown, Short Tail)

When these genotypes are grouped by phenotype, the expected ratio is 9:3:3:1, where 9 is gray fur with a long tail, 3 is gray fur with a short tail, 3 is brown fur with a long tail, and 1 is brown fur with a short tail. This assumes that there are no other genetic factors influencing these traits, such as epistasis.

Answer 2

Step-by-step explanation:

In this cross, the two parent mice are heterozygous for both the fur and tail traits, which means that they have the genotypes GgLl. The offspring of this cross will have a 1/4 chance of inheriting a GgLl genotype, a 1/4 chance of inheriting a Ggll genotype, a 1/4 chance of inheriting a ggLl genotype, and a 1/4 chance of inheriting a ggll genotype.

The expected phenotype ratio of the offspring will depend on which traits are dominant and which are recessive. In this case, the G allele is dominant and the g allele is recessive for the fur trait, and the L allele is dominant and the l allele is recessive for the tail trait. Therefore, the expected phenotype ratio of the offspring will be as follows:

Phenotype Ratio

Gray, long tail: 1/4

Gray, short tail: 1/4

Brown, long tail: 1/4

Brown, short tail: 1/4

This means that the expected phenotype ratio of the offspring is 1:1:1:1, or a 1:1 ratio of gray to brown fur and a 1:1 ratio of long to short tails.