Question

У дрозофилы рецессивный ген белоглазия w - мутация white - локализован в Х-хромосоме. Мухе дикого типа имеют красные глаза.Гомозиготная красноглазая самка скрещена с белоглазым самцом. Определите цвет глаз у самок и самцов в первом и втором поколениях. Напишите схему скрещивания, показав локализацию генов а хромосомах.

Answer 1

                                                                 

Answer 2

Introduction

In Drosophila (fruit flies), the recessive gene for white eye color, denoted as w, is a mutation of the wild-type red eye color gene. The white eye color gene is located on the X chromosome. In this scenario, a homozygous red-eyed female is crossed with a white-eyed male. We need to determine the eye color of the offspring in the first and second generations and provide a breeding scheme showing the gene localization on the chromosomes.

Eye Color in the First Generation

When a homozygous red-eyed female (XX) is crossed with a white-eyed male (XwY), the offspring will inherit one X chromosome from the female and one sex chromosome from the male. The possible genotypes and corresponding eye colors in the first generation are as follows:

- Female offspring: - XwXw genotype (white-eyed) - 50% chance - XX genotype (red-eyed) - 50% chance

- Male offspring: - XwY genotype (white-eyed) - 100% chance

Therefore, in the first generation, there is a 50% chance of having white-eyed females, a 50% chance of having red-eyed females, and all males will have white eyes.

Eye Color in the Second Generation

To determine the eye color in the second generation, we need to consider the eye color of the first-generation offspring. Let's assume that a white-eyed female (XwXw) from the first generation is crossed with a red-eyed male (XRY) from the wild-type population. The possible genotypes and corresponding eye colors in the second generation are as follows:

- Female offspring: - XwX genotype (red-eyed) - 50% chance - XX genotype (red-eyed) - 50% chance

- Male offspring: - XwY genotype (white-eyed) - 50% chance - XY genotype (red-eyed) - 50% chance

Therefore, in the second generation, there is a 50% chance of having red-eyed females, a 50% chance of having red-eyed males, and a 50% chance of having white-eyed males.

Breeding Scheme and Gene Localization

The breeding scheme for the given scenario can be represented as follows:

1st Generation: - Homozygous red-eyed female (XX) x White-eyed male (XwY)

2nd Generation: - White-eyed female (XwXw) x Red-eyed male (XRY)

The gene for white eye color (w) is located on the X chromosome. In the first generation, the female offspring will inherit one X chromosome from the female parent and one sex chromosome from the male parent. The male offspring will inherit one X chromosome from the female parent and one Y chromosome from the male parent.

In the second generation, the white-eyed female (XwXw) will pass on one X chromosome to her offspring, while the red-eyed male (XRY) will pass on either an X or Y chromosome to his offspring.

Please note that the breeding scheme and gene localization are based on the given information and assumptions made for this specific scenario.