Question

У собак доминантная аллель гена А обуславливает черную масть, рецессивная аллель а — коричневую. Доминантный ген-ингибитор I подавляет проявление действия обоих генов и обуславливает белую масть. Рецессивная аллель гена-ингибитора i не оказывает влияния на окраску шерсти. Какое потомство можно ожидать от скрещивания гетерозиготной черной собаки с дигетерозиготной белой?

Answer 1

А- черная, а-коричневая, І- белая, і- не несёт. 
гетерозиготная черная собака - Ааіі
дигетерозиготная белая - АаІі
P: Aaii   x     AaIi
G: Ai, ai       AI,Ai,aI,ai
F: AAIi(бел), AAii(черн), AaIi(бел), Aaii(черн)
    AaIi(бел), Aaii(черн), aaIi(бел). aaii(кор)
4 бел : 3 черн : 1 кор = 50% : 37,5% : 12,5%

Answer 2

Inheritance of Coat Color in Dogs

In dogs, the coat color is determined by the interaction of different alleles of specific genes. The major genes involved in coat color inheritance are the A locus (agouti locus) and the I locus (inhibitor locus).

- The dominant allele of the A locus, gene A, determines black coat color. - The recessive allele of the A locus, gene a, determines brown coat color. - The dominant gene at the I locus, gene I, inhibits the expression of both the A and a genes, resulting in a white coat color. - The recessive gene at the I locus, gene i, does not affect the coat color.

When a black dog that is heterozygous (carries one copy of the dominant black allele and one copy of the recessive brown allele) is crossed with a white dog that is heterozygous (carries one copy of the dominant white allele and one copy of the recessive non-white allele), the possible offspring can be determined using Punnett squares.

Punnett Square Analysis

Let's represent the black coat color allele (A) as B and the brown coat color allele (a) as b. Similarly, let's represent the dominant white allele (I) as W and the recessive non-white allele (i) as w.

The genotype of the black dog is BbIi, and the genotype of the white dog is BBii.

| | BbIi | Bbii | |---------|------|------| | BBii | BbIi | Bbii | | BbIi | BbIi | Bbii |

From the Punnett square, we can see that the possible genotypes of the offspring are BbIi and Bbii.

- The BbIi genotype represents a black dog with a heterozygous genotype for both coat color and white inhibition. - The Bbii genotype represents a black dog with a heterozygous genotype for coat color and a homozygous recessive genotype for white inhibition.

Therefore, the expected offspring from the cross between a heterozygous black dog and a heterozygous white dog would be black dogs with a mix of heterozygous and homozygous recessive genotypes for coat color and white inhibition.

It's important to note that this is a simplified explanation of coat color inheritance in dogs, and there may be other genes and factors that can influence coat color variations.