Using the information provided in Problems 10 and 11, determine the genotype and phenotype of parents that produce the following progeny:
27/64 brown : 16/64 albino : 9/64 yellow : 9/64 black : 3/64 cream

Verified step by step guidance

1. Analyze the phenotypic ratio of the progeny (27:16:9:9:3) and compare it to known Mendelian inheritance patterns. This suggests a dihybrid cross involving two genes with epistasis.
2. Assign symbols to the genes involved. For example, let Gene A control pigment production (A = pigment, a = no pigment) and Gene B control pigment color (B = brown, b = yellow). Albino phenotype occurs when Gene A is homozygous recessive (aa), masking the effect of Gene B.
3. Determine the genotypes responsible for each phenotype: Brown (A-B-), Albino (aa--), Yellow (A-bb), Black (A-Bb), and Cream (AAbb). The phenotypic ratios align with these genotypes under a dihybrid cross with epistasis.
4. Identify the parental genotypes that could produce the observed progeny ratios. A likely combination is AaBb x AaBb, as this would produce the expected 9:3:3:1 ratio modified by epistasis to match the observed 27:16:9:9:3 ratio.
5. Verify the hypothesis by constructing a Punnett square for the cross AaBb x AaBb, considering the epistatic interaction between the two genes. Check that the resulting genotypic and phenotypic ratios align with the observed progeny distribution.

Key Concepts

Genotype

Genotype refers to the genetic constitution of an organism, specifically the alleles it possesses for a particular trait. In this context, understanding the genotype is crucial for predicting the phenotypic ratios of the progeny. The genotype can be homozygous (two identical alleles) or heterozygous (two different alleles), and it directly influences the observable traits in the offspring.

Phenotype

Phenotype is the observable physical or biochemical characteristics of an organism, determined by both its genotype and environmental factors. In this question, the phenotypic ratios of the progeny (brown, albino, yellow, black, and cream) provide insight into the genetic makeup of the parents. Analyzing these ratios helps in deducing the possible genotypes that could lead to such offspring.

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 setting up a Punnett Square with the potential genotypes of the parents, one can calculate the expected phenotypic ratios, which is essential for solving the given problem.