Question

In sheep, the allele for belly fur (A) is dominant to the allele for no belly fur (a). A heterozygous mother and a heterozygous father are crossed. What are the percentages of the genotypes of an offspring?

A) The percentages of the genotypes of the offspring from a heterozygous mother and father are...
B) Calculate the likelihood of each genotype in the offspring when both parents are heterozygous for belly fur.
C) The genotype percentages in the offspring's population are...
D) Explain how to determine the percentages of genotypes in the offspring when the parents are heterozygous for belly fur.

Answer 1

In a Punnett square cross of heterozygous parents with genotypes Aa for sheep belly fur, offspring have a 25% chance of being homozygous dominant (AA), 50% of being heterozygous (Aa), and 25% of being homozygous recessive (aa).

Step-by-step explanation:

To calculate the likelihood of each genotype for offspring when both parents are heterozygous for belly fur in sheep, we can use a Punnett square. With the dominant allele for belly fur being A and the recessive allele being a, the possible genotypes of the parents are Aa. By crossing two heterozygous parents (Aa x Aa), the genotypes of the offspring will be AA (homozygous dominant), Aa (heterozygous), and aa (homozygous recessive), with expected ratios of 1:2:1. This means there is a 25% chance for AA, a 50% chance for Aa, and a 25% chance for aa.

These percentages reflect the genotypic frequency of the offspring from heterozygous parents:

• Homozygous dominant (AA): 25%
• Heterozygous (Aa): 50%
• Homozygous recessive (aa): 25%

To determine these percentages, we apply the principles of Mendelian genetics, considering the random segregation of alleles and the probability of different combinations from the gene pool. When predicting a large number of crosses, the actual ratio of genotypes will approach these expected values.