Using the information provided in Problems 10 and 11, determine the genotype and phenotype of parents that produce the following progeny:
3/4 brown : 1/4 yellow

Verified step by step guidance

1. Step 1: Begin by analyzing the progeny ratio provided in the problem. The ratio of 3/4 brown to 1/4 yellow suggests a Mendelian inheritance pattern consistent with a single gene exhibiting dominance and recessiveness. Brown is likely the dominant phenotype, and yellow is the recessive phenotype.
2. Step 2: Recall that a 3:1 phenotypic ratio typically arises from a monohybrid cross where both parents are heterozygous for the gene in question. Represent the dominant allele as 'B' (brown) and the recessive allele as 'b' (yellow). The heterozygous genotype would be 'Bb'.
3. Step 3: Set up a Punnett square to confirm the expected progeny ratios. Place the alleles of one parent (B and b) along the top of the square and the alleles of the other parent (B and b) along the side. Fill in the squares by combining the alleles from the top and side.
4. Step 4: Analyze the Punnett square results. You should observe that the genotypes of the progeny are distributed as follows: 1/4 BB (homozygous dominant), 1/2 Bb (heterozygous), and 1/4 bb (homozygous recessive). The phenotypes will be 3/4 brown (BB and Bb) and 1/4 yellow (bb).
5. Step 5: Conclude that the parents must both have the genotype 'Bb' (heterozygous) to produce the observed 3:1 phenotypic ratio in the progeny. Their phenotypes would both be brown, as the dominant allele masks the recessive allele in heterozygous individuals.

Key Concepts

Genotype

Genotype refers to the genetic constitution of an organism, specifically the alleles it possesses for a particular trait. In this context, it is important to understand how different combinations of alleles can lead to the observed phenotypes in progeny. For example, in a simple Mendelian trait, the genotype can be homozygous dominant, homozygous recessive, or heterozygous, influencing the traits expressed 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 case, the phenotypes of the progeny are brown and yellow, which are the visible traits resulting from the underlying genotypes of the parents. Understanding the relationship between genotype and phenotype is crucial for predicting the traits of offspring.

Mendelian Inheritance

Mendelian inheritance is the set of principles related to the transmission of genetic traits from parents to offspring, based on Gregor Mendel's experiments with pea plants. The ratios of phenotypes in the progeny, such as 3:1 in this case, suggest a typical monohybrid cross where one trait is dominant over another. This concept helps in predicting the expected ratios of offspring based on the genotypes of the parents.