Consider the cross AaBbCC × AABbCc.
Use the forked-line method to predict the expected ratio of offspring phenotypes.

Verified step by step guidance

1. Step 1: Break down the problem into individual gene pairs. For each gene pair, determine the possible genotypes and their probabilities. For example, for the Aa × AA cross, the possible offspring genotypes are AA and Aa, with probabilities of 1/2 and 1/2 respectively.
2. Step 2: Repeat the process for the Bb × Bb cross. The possible offspring genotypes are BB, Bb, and bb, with probabilities of 1/4, 1/2, and 1/4 respectively.
3. Step 3: Analyze the CC × Cc cross. The possible offspring genotypes are CC and Cc, with probabilities of 1/2 and 1/2 respectively.
4. Step 4: Use the forked-line method to combine the probabilities of each gene pair. Multiply the probabilities of each genotype across the three gene pairs to determine the overall probabilities for each combination of genotypes.
5. Step 5: Translate the genotypes into phenotypes based on dominance relationships for each gene. Group the offspring into phenotypic categories and sum the probabilities for each phenotype to predict the expected ratio of offspring phenotypes.

Key Concepts

Forked-Line Method

The forked-line method is a visual tool used in genetics to predict the genotypic and phenotypic ratios of offspring from a genetic cross. It involves breaking down the inheritance of each gene independently and then combining the results to find the overall ratios. This method simplifies complex crosses by allowing for the systematic organization of possible allele combinations.

Phenotype

A phenotype refers to the observable characteristics or traits of an organism, which result from the interaction of its genotype with the environment. In genetics, phenotypes can include physical traits like color, shape, and size, as well as behavioral traits. Understanding phenotypes is crucial for predicting the outcomes of genetic crosses, as they represent the traits that will be expressed in the offspring.

Dihybrid Cross

A dihybrid cross involves two traits, each controlled by different genes, and examines the inheritance patterns of these traits simultaneously. In the given cross, AaBbCC × AABbCc, the presence of multiple alleles for two traits allows for a more complex analysis of offspring ratios. The expected phenotypic ratios from a dihybrid cross can often be predicted using the principles of independent assortment and segregation.