In chickens, the Leghorn variety has white feathers due to an autosomal dominant allele. Silkies have white feathers due to recessive allele in a second gene. If true-breeding white leghorn is crossed to a true breeding white silkie, What is the expeected phenotype of the F1 generation? If member of the F1 generation are mated to each other, what is the expected phenotypic outcome of the F2 generations. Assumes that the parental generations are homozygous brown allele and the other is the homozzygous white allele. In subsequent generations, nonwhite birds will be brown.
I am respone
To determine the expected phenotypes of the F1 generation and the F2 generation, we need to understand the inheritance patterns and the genotypes of the parents in this cross.
According to the information provided, the Leghorn variety's white feathers are determined by an autosomal dominant allele, while the white feathers in Silkies are due to a recessive allele in a different gene.
The true-breeding white Leghorn is homozygous for the dominant white allele (WW), and the true-breeding white Silkie is homozygous for the recessive white allele (ww).
1. F1 Generation:
When these two true-breeding parents are crossed (WW x ww), all the offspring (F1 generation) will be heterozygous for both genes (WwWw). In other words, they will carry one dominant white allele (W) and one recessive white allele (w).
The expected phenotype of the F1 generation will be white feathers because the presence of the dominant white allele (W) from the Leghorn parent will mask the expression of the recessive white allele (w) from the Silkie parent.
2. F2 Generation:
When members of the F1 generation are mated with each other (WwWw x WwWw), the possible genotypes that can result from this cross are WW, Ww, and ww in a 1:2:1 ratio.
The expected phenotypic outcome of the F2 generation will be as follows:
- 25% will have the genotype WW and show the white phenotype.
- 50% will have the genotype Ww and also exhibit the white phenotype due to the dominant white allele (W) overshadowing the recessive allele (w).
- 25% will have the genotype ww and display the brown phenotype since they inherit two copies of the recessive allele from both parents.
Therefore, in subsequent generations, the non-white birds will have brown feathers, as stated in the question.
In summary:
- F1 generation: All white phenotype (WwWw).
- F2 generation: 75% white phenotype (combination of WW and Ww) and 25% brown phenotype (ww).