Question

Отсутствие малых коренных зубов у человека наследуется как доминантный признак .Определите генотипы и фенотипы родителей и потомства, если супруги имеют малые коренные зубы и гетерозиготны по этому признаку. Какова вероятность рождения детей с этой аномалией? Как изменится вероятность, если один из родителей полностью рецесивен?

Answer 1

АА - отсутствие малых коренных зубов
Аа - малые коренные зубы есть, но является носителем гена
аа - здоров, малые коренные зубы есть

♂Аа х ♀Аа = АА(малые коренные зубы отстутствуют) : Аа(малые коренные зубы есть, но носители гена) : аа (здоров)

Answer 2

Understanding the Inheritance of Small Roots Anomaly

The inheritance of the small roots anomaly in humans is a topic of genetic interest. Let's delve into the genotypes and phenotypes of the parents and offspring, as well as the probability of children being born with this anomaly.

Genotypes and Phenotypes of the Parents and Offspring

If the spouses have small roots and are heterozygous for this trait, we can determine their genotypes and phenotypes. The small roots anomaly is inherited as a dominant trait.

- Genotypes: - The genotype of each parent can be represented as Ss, where S denotes the dominant allele for small roots, and s denotes the recessive allele for normal roots. - As both parents are heterozygous, their genotypes are Ss.

- Phenotypes: - The phenotype of individuals with the Ss genotype will exhibit the dominant trait, which is having small roots.

For the offspring: - The Punnett square for the cross between two heterozygous parents (Ss x Ss) would yield the following genotypic and phenotypic ratios: - Genotypic ratio: 1 SS : 2 Ss : 1 ss - Phenotypic ratio: 3 small roots : 1 normal roots

Probability of Offspring with the Anomaly

The probability of the children being born with the small roots anomaly can be calculated from the Punnett square ratios: - The probability of a child having small roots (SS or Ss genotype) is 3/4 or 75%. - The probability of a child having normal roots (ss genotype) is 1/4 or 25%.

Impact of One Parent Being Completely Recessive

If one of the parents is completely recessive (ss genotype), the genotypic and phenotypic outcomes change: - The genotype of the recessive parent is ss. - The genotype of the heterozygous parent is Ss.

The Punnett square for this cross would yield the following genotypic and phenotypic ratios: - Genotypic ratio: 2 Ss : 2 ss - Phenotypic ratio: 2 small roots : 2 normal roots

The probability of the children having the small roots anomaly in this scenario is 50%.

In summary, when both parents are heterozygous for the small roots anomaly, there is a 75% chance of their children having this anomaly. However, if one parent is completely recessive, the probability decreases to 50%.