Question

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 )

Answer 1

25%

Step-by-step 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.