In rabbits, black hair depends on a dominant allele, B, and brown hair on a recessive allele, b. Short hair is due to a dominant allele, S, and long hair to a recessive allele, s. If a true-breeding black short-haired male is mated with a brown long-haired female, describe their offspring. What will be the genotypes of the offspring? If two of these F1 rabbits are mated, what phenotypes would you expect among their offspring? In what proportions?

Verified step by step guidance

1. Identify the genotypes of the parent rabbits. A true-breeding black short-haired male would have the genotype BBSS, as black hair (B) and short hair (S) are dominant traits. A brown long-haired female would have the genotype bbss, as brown hair (b) and long hair (s) are recessive traits.
2. Determine the gametes produced by each parent. The male can only produce B S gametes due to his homozygous dominant genotype. The female can only produce b s gametes due to her homozygous recessive genotype.
3. Perform a Punnett square using the gametes from each parent to find the genotypes of the F1 generation. Since the male produces only B S gametes and the female produces only b s gametes, all F1 offspring will have the genotype BbSs.
4. Analyze the F1 generation's genotype (BbSs) to determine their phenotype. Bb results in black hair since B is dominant over b, and Ss results in short hair since S is dominant over s. Thus, all F1 offspring will be black and short-haired.
5. Predict the phenotypes of the F2 generation by mating two F1 rabbits (BbSs x BbSs). Use a Punnett square to determine the possible genotypes and corresponding phenotypes, considering both traits (hair color and hair length). Calculate the phenotypic ratios to determine the proportions of each phenotype among the F2 offspring.

Key Concepts

Mendelian Genetics

Mendelian genetics is the study of how traits are inherited through generations based on the principles established by Gregor Mendel. It involves understanding dominant and recessive alleles, where dominant alleles mask the expression of recessive ones. In this scenario, the traits of hair color and length in rabbits are determined by specific alleles, with 'B' and 'S' being dominant and 'b' and 's' being recessive.

Genotype and Phenotype

The genotype refers to the genetic makeup of an organism, specifically the alleles it possesses for a particular trait, while the phenotype is the observable expression of those traits. For example, a rabbit with the genotype 'BB' or 'Bb' will exhibit a black fur phenotype, whereas 'bb' will result in brown fur. Understanding the relationship between genotype and phenotype is crucial for predicting the traits of offspring in genetic crosses.

Punnett Square

A Punnett square is a diagram used to predict the genetic outcomes of a cross between two organisms. It allows for the visualization of how alleles from each parent combine to form the genotypes of the offspring. By filling out the Punnett square for the given parental genotypes, one can determine the expected proportions of different phenotypes in the offspring, aiding in the understanding of inheritance patterns.