Black plumage in chickens dominates brown and crested over the absence of crest. These traits are inherited

Black plumage in chickens dominates brown and crested over the absence of crest. These traits are inherited independently. Brown hens without a crest were crossed with purebred black crested roosters. Obtaining hybrids of the first generation crossed among themselves and gave 400 chickens “1) How many types of gametes are formed in a hybrid of the first generation? 2) How many different genotypes are there among the black chickens of the second generation? 3) How many black chickens are received in the second generation? 4) How many brown chickens are received in the second generation? 5) How many different genotypes are among the rugged crested chickens?

According to the condition of the problem, let us designate the gene that causes the black color of the plumage of chickens as A, then the gene for the brown color of the plumage will be a. Let’s designate the gene that determines the presence of the crest as C, then the gene for its absence will be c.

Brown hens without a crest will be aass, because the indicated phenotype is realized only in the condition of homozygosity. They produce ac oocytes.

Black crested males are pure breed, therefore, they are homozygous – AACC. These males produce AС sperm.

When crossing brown chickens without a crest with the described roosters, all offspring will be AaCc, have crests and black plumage.

The sex cells produced by such hybrids will look like this: AC, ac, aC and Ac. In total – 4.

The offspring obtained by crossing such chickens and roosters are presented:

black crested chickens (ААСС, 4 АаСс, 2 АаСС, 2 ААСс);

brown chickens without a crest (aass);

brown crested chickens (2 ааСс, ааСС);

black chickens without crest (2 Aass, Aass).

The number of genotypes is 16.

Black chickens in the second generation – (12 * 400) / 16 = 300.

Brown chickens in the second generation – (4 * 400) / 16 = 100.

2 different genotypes of brown chickens: aaCc and aacC.