homozygous line of normal-hearing dogs was crossed with a homozygous line of deaf dogs. F1 and F2 generations were produced. What percent of F1 generation is expected to have normal hearing?
What is a phenoeyeic ratio of the F2 generation?
I answered this question, and the second is incomplete.
There are three types of progeny in the F1 generation, and the question doesn't specify which progeny.
To determine the percent of the F1 generation expected to have normal hearing, we need to understand the inheritance pattern of the trait.
In this case, we have a cross between a homozygous line of normal-hearing dogs ("NN") and a homozygous line of deaf dogs ("dd"). The capital letter "N" represents the dominant allele for normal hearing, while the lowercase letter "d" represents the recessive allele for deafness.
When these two homozygous lines are crossed, all the F1 progeny will be heterozygous for the trait and will have one copy of the normal allele and one copy of the deafness allele ("Nd").
To calculate the percentage of F1 individuals with normal hearing, we need to know the proportion of individuals with the normal allele ("Nd" or "NN") in the F1 generation. Since all F1 individuals have the "Nd" genotype, the answer is 100%. Therefore, all the F1 generation dogs are expected to have normal hearing.
Moving on to the F2 generation, we need to know the phenotypic ratio. A phenotypic ratio describes the ratio of observable traits in a population resulting from a particular cross.
In this case, we know that all the F1 individuals are heterozygous ("Nd") for the hearing trait. When these individuals are crossed with each other, there are three possible genotypes in the F2 generation: "NN", "Nd", and "dd".
The genotypic ratio of the F2 generation is expected to be 1:2:1. This means that for every one individual with the "NN" genotype (normal hearing), there will be two individuals with the "Nd" genotype (carrier of deafness), and one individual with the "dd" genotype (deaf).
The phenotypic ratio can be determined by considering the expression of the deafness trait. Since it is a recessive trait, an individual needs to have two copies of the deafness allele ("dd") to exhibit the deaf phenotype. Thus, the phenotypic ratio for the F2 generation will be 3:1, with three individuals expected to have normal hearing and one individual expected to be deaf.