Question

Врожденная близорукость наследуется как аутосомный доминантный признак, отсутствие веснушек – как аутосомный рецессивный признак. Признаки находятся в разных парах хромосом. У отца врожденная близорукость и отсутствие веснушек, у матери нормальное зрение и веснушки. В семье трое детей, двое близорукие без веснушек, один с нормальным зрением и с веснушками. Составьте схему решения задачи. Определите генотипы родителей и родившихся детей. Рассчитайте вероятность рождения детей близоруких и с веснушками. Объясните, какой закон имеет место в данном случае.

Answer 1

Близорукость-А
норм.зрение-а
отсутствие веснушек-b
веснушчатость-В
Решение:
P: (мать)ааВb    х  (отец)Ааbb  
G:    aB,ab               Ab,ab    
F: AaBb(близор,веснуш), Aabb(близор,без веснуш), aaBb(норм.зр,веснуш), aabb(норм.зр,без веснуш)
Вероятность рождения детей близоруких-50% и с веснушками-50%
В данной задачи имеет место закон независимого наследования признаков(третий закон Менделя).

Answer 2

Problem Analysis and Solution Schema

To solve this problem, we need to determine the genotypes of the parents and the children, calculate the probability of the children being nearsighted and freckled, and explain the law that applies in this case.

1. Genotypes of Parents and Children: - Father: Nearsighted and freckle-free - Mother: Normal vision and freckles - Three children: Two nearsighted without freckles, one with normal vision and freckles

2. Solution Schema: - Determine the genotypes of the parents and children based on the given information. - Use the genotypes to calculate the probability of the children being nearsighted and freckled. - Explain the law that applies to this inheritance pattern.

Genotypes of Parents and Children

The inheritance pattern of nearsightedness as an autosomal dominant trait and the absence of freckles as an autosomal recessive trait can be used to determine the genotypes of the parents and children.

1. Father's Genotype: - Since nearsightedness is an autosomal dominant trait and the father is nearsighted, his genotype is Nn (where N represents the dominant allele for nearsightedness).

2. Mother's Genotype: - The mother has normal vision and freckles, so she must be nn for nearsightedness and FF for freckles (where F represents the dominant allele for freckles).

3. Children's Genotypes: - Two nearsighted children without freckles: Nn nn - One child with normal vision and freckles: nn FF

Probability of Nearsighted and Freckled Children

To calculate the probability of the children being nearsighted and freckled, we can use Punnett squares to determine the possible genotypes of the offspring.

1. Probability of Nearsighted Children: - Since nearsightedness is an autosomal dominant trait, the probability of the children being nearsighted is 100% for the offspring of a nearsighted parent.

2. Probability of Freckled Children: - Since the mother is homozygous dominant for freckles (FF), all the children will inherit the dominant allele for freckles, resulting in 100% probability of the children having freckles.

Law Applicable to this Case

The law of independent assortment applies to this case. This law states that different genes separate independently of one another during gamete formation. In this scenario, the inheritance of nearsightedness and freckles is independent of each other due to the genes being located on different pairs of autosomal chromosomes. As a result, the inheritance of one trait does not influence the inheritance of the other trait.

This analysis provides a comprehensive understanding of the genotypes of the parents and children, the probability of the children inheriting specific traits, and the law that governs the inheritance pattern in this case.