In mice, grey fur is dominant over albino (white) fur. A homozygous grey-furred mouse is crossed with an albino mouse.a) what are the alleles for this trait? (1)
b) what are the genotypes of the parent mice? (2)
c) do a Punnett Square, and write the genotype and phenotype ratios of the offspring (F1).
a) The alleles for fur color in mice are represented by symbols. In this case, grey fur (dominant trait) will be represented by the letter "G," and albino (recessive trait) will be represented by the letter "g."
b) To determine the genotypes of the parent mice, we need to understand the meaning of homozygous and albino. Homozygous refers to having two identical alleles for a particular trait, while albino refers to having two recessive alleles.
Given the information that a homozygous grey-furred mouse is crossed with an albino mouse, we can represent the genotypes of the parent mice as follows:
- Homozygous grey-furred mouse: GG (Both alleles are dominant, for grey fur)
- Albino mouse: gg (Both alleles are recessive, for albino fur)
c) To create a Punnett Square, we'll represent one parent's alleles vertically and the other parent's alleles horizontally, and then combine them to see the possible combinations in the offspring.
| G | G |
------------
g | Gg | Gg |
In this case, all offspring will inherit one "G" allele from the homozygous grey-furred mouse (GG) and one "g" allele from the albino mouse (gg). Therefore, all of the offspring (F1) will have the genotype Gg.
Regarding the phenotype ratios, since the grey fur color is dominant, the presence of even one "G" allele will result in a grey phenotype. Hence, all the offspring will have grey fur.
Therefore, the genotype ratio is 100% Gg, and the phenotype ratio is 100% grey fur.