In rats, the allele for long whiskers is dominant to the allele for short whiskers. At another gene locus, a dominant allele produces whiskers and the recessive allele produces a rat with no whiskers. The alleles at these 2 gene loci assort independently. If a rat that is homozygous for both recessive alleles is crossed with a rat that is heterozygous at both gene loci, what percentage of the offspring are expected to have short whiskers? (Enter the number only without the percent sign. For example, enter 100% as 100 and enter 12.5% as 12.5)

Question

Hector Travis

Biology

8 March, 18:54

In rats, the allele for long whiskers is dominant to the allele for short whiskers. At another gene locus, a dominant allele produces whiskers and the recessive allele produces a rat with no whiskers. The alleles at these 2 gene loci assort independently. If a rat that is homozygous for both recessive alleles is crossed with a rat that is heterozygous at both gene loci, what percentage of the offspring are expected to have short whiskers? (Enter the number only without the percent sign. For example, enter 100% as 100 and enter 12.5% as 12.5)

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Caleb Tate · Answer 1

25%

Explanation:

We have 2 independent genes with 2 alleles each: L/l and W/w

W_: whiskers ww: no whiskers L_: long whiskers ll: short wiskers

Individuals with short whiskers will have the genotype WWll or Wwll.

A cross between a rat heterozygous for both genes and a homozygous recessive rat is done:

WwLl x wwll

-The homozygous rat will produce only wl gametes.

-The heterozygous rat will produce the following gametes: WL, Wl, wL, wl.

If you do a Punnett Square, you'll get that 25% of the offspring will be WwLl and will have short whiskers.