In rabbits, albinism is an autosomal recessive condition caused by the absence of the pigment melanin from skin and fur. Pigmentation is a dominant wild-type trait. Three pure-breeding strains of albino rabbits, identified as strains 1, 2, and 3, are crossed to one another. In the table below, F₁ and F₂ progeny are shown for each cross. Based on the available data, propose a genetic explanation for the results. As part of your answer, create genotypes for each albino strain using clearly defined symbols of your own choosing. Use your symbols to diagram each cross, giving the F₁ and F₂ genotypes. <>

Key Concepts

Autosomal Recessive Inheritance

Autosomal recessive inheritance refers to a pattern where a trait is expressed only when an individual has two copies of the recessive allele. In the case of albinism in rabbits, the absence of melanin is due to the recessive allele, meaning that only rabbits with two copies of this allele (aa) will exhibit the albino phenotype. If an individual has at least one dominant allele (A), they will display the wild-type pigmentation.

Pure-Breeding Strains

Pure-breeding strains are genetically uniform populations that consistently produce offspring with the same phenotype when crossed. In this scenario, the three pure-breeding albino strains (1, 2, and 3) are homozygous for the recessive allele (aa). When these strains are crossed, the resulting F₁ generation will all be heterozygous (Aa), displaying the dominant wild-type trait, while the F₂ generation will show a phenotypic ratio based on Mendelian inheritance.

Punnett Squares and Genetic Diagrams

Punnett squares are tools used to predict the genotypes and phenotypes of offspring from genetic crosses. By diagramming the crosses between the different albino strains, one can visualize the inheritance patterns and calculate the expected ratios of genotypes in the F₁ and F₂ generations. This method helps clarify how the alleles segregate and combine, providing a clear genetic explanation for the observed results in the progeny.