Question

Suppose the ear length of two populations of jerboas is controlled by one gene. To determine the mode of inheritance, a homozygous short‑eared female is crossed with a homozygous long‑eared male. Then, siblings from the F1 are crossed, and the number of short‑ and long‑eared animals are counted to determine the phenotype ratio. Match the phenotypic ratio anticipated in the offspring from a cross of two heterozygous individuals to the appropriate mode of inheritance for the short‑ear allele.

Answer 1

Answer:

The short‑ear allele phenotypic ratio is 25%.

Explanation:

Genotype for homozygous short‑eared progenitor: ll

Genotype for homozygous long-eared progenitor: LL

Genotype for heterozygous: Ll

P)                                                LL x ll

Gametes)                             L     L       l       l

F1)                                                  LlLl

All of the individuals of the first progeny are long-eared heterozygote.

The cross of two heterozygous individuals:

                                                  Ll  x Ll

Gametes)                                L   l      L   l

F2)                                     25% Homozygote for the long ear: LL

                                          25% Homozygote for the short ear: ll

                                          50% Heterozygote: Ll

                                           75% of progeny are Longed-ear animals

                                          25% of progeny are Shorted-ear animals