Question

У коров безрогость доминирует над рогатостью. При скрещивании гомозиготных безрогих животных с рогатыми было получено 96 гибридов. После скрещивания гибридов между собой в F2 получили 48 телята) Сколько гетерозиготных животных среди гибридов F1?б) Сколько разных генотипов среди гибридов F2?в) Сколько фенотипов среди гибридов F2?г) Сколько будет безрогих животных в F2?д) Сколько будет рогатых животных в F2?

Answer 1

A - bezrogost

a - rogatost

 

P   : AA x aa

F1 : Aa ; Aa ; Aa ; Aa (96 gibridov)

 

P   : Aa x Aa

F2 : AA ; Aa ; Aa ; aa (48 telyat)

 

a) vse otpryski v F1 budut geterozigotnymi, toest ih 96

b) 3 (AA ; Aa ; aa)

c) 2 - bezrogiye (AA ; Aa) i rogatye (aa)

d) 3/4 (AA ; Aa) , 48*3/4 = 36

e) 1/4 (aa) , 48*1/4 = 12

Answer 2

Background Information

In cattle, the presence or absence of horns is determined by a genetic trait. The gene responsible for horned or polled (hornless) phenotype is known as the "polled" gene. The polled gene is dominant over the horned gene, meaning that if an animal inherits the polled gene from either parent, it will be polled. However, if an animal inherits the horned gene from both parents, it will have horns.

Given Information

- When homozygous polled (without horns) animals were crossed with horned animals, 96 hybrids were obtained. - The hybrids from the F1 generation were crossed with each other, resulting in 48 calves in the F2 generation.

Calculating the Answers

a) Number of heterozygous animals among the F1 hybrids: To determine the number of heterozygous animals (carrying one polled and one horned gene) among the F1 hybrids, we need to subtract the number of homozygous polled animals from the total number of hybrids obtained in the F1 generation.

Let's assume the number of homozygous polled animals in the F1 generation is x. Since the total number of hybrids obtained in the F1 generation is 96, we can set up the following equation:

x + heterozygous animals = 96

Since the homozygous polled animals are crossed with horned animals, all the hybrids in the F1 generation will be heterozygous. Therefore, the number of heterozygous animals among the F1 hybrids is 96 - x.

b) Number of different genotypes among the F2 hybrids: To determine the number of different genotypes among the F2 hybrids, we need to consider the possible combinations of genes from the F1 hybrids.

In the F1 generation, all the hybrids are heterozygous, carrying one polled gene and one horned gene. When these F1 hybrids are crossed with each other, the possible genotypes in the F2 generation are:

- Homozygous polled (PP): 1/4 of the offspring - Heterozygous polled (Pp): 1/2 of the offspring - Homozygous horned (pp): 1/4 of the offspring

Therefore, there are three different genotypes among the F2 hybrids.

c) Number of different phenotypes among the F2 hybrids: The phenotypes of the F2 hybrids are determined by the expression of the genes they inherit. In this case, the polled gene is dominant over the horned gene.

- Homozygous polled (PP): These animals will be polled. - Heterozygous polled (Pp): These animals will also be polled because the polled gene is dominant. - Homozygous horned (pp): These animals will have horns.

Therefore, there are two different phenotypes among the F2 hybrids: polled and horned.

d) Number of polled animals in the F2 generation: To determine the number of polled animals in the F2 generation, we need to consider the genotypes and their corresponding phenotypes.

In the F2 generation, the possible genotypes are: - Homozygous polled (PP): 1/4 of the offspring - Heterozygous polled (Pp): 1/2 of the offspring

Since both genotypes result in the polled phenotype, the total number of polled animals in the F2 generation is:

(1/4) * 48 (number of calves in F2) + (1/2) * 48 (number of calves in F2)

e) Number of horned animals in the F2 generation: To determine the number of horned animals in the F2 generation, we need to consider the genotypes and their corresponding phenotypes.

In the F2 generation, the possible genotype is: - Homozygous horned (pp): 1/4 of the offspring

Since this genotype results in the horned phenotype, the total number of horned animals in the F2 generation is:

(1/4) * 48 (number of calves in F2)

Please note that the specific values for the number of heterozygous animals in the F1 generation and the number of polled and horned animals in the F2 generation cannot be determined without additional information.