Mendel crossed peas having round green seeds with peas having wrinkled yellow seeds. All F₁ plants had seeds that were round and yellow. Predict the results of testcrossing these F₁ plants.

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 traits mask the expression of recessive ones. In this case, round seeds (R) are dominant over wrinkled seeds (r), and yellow seeds (Y) are dominant over green seeds (y).

Testcross

A testcross is a genetic cross performed to determine the genotype of an individual expressing a dominant phenotype. This is done by crossing the individual with a homozygous recessive individual. In the context of the F₁ plants, a testcross will reveal whether the round yellow seeds are homozygous dominant (RRYY) or heterozygous (RrYy) based on the phenotypes of the offspring.

Phenotypic Ratios

Phenotypic ratios describe the relative frequencies of different phenotypes in the offspring resulting from a genetic cross. In a testcross involving the F₁ plants, the expected phenotypic ratio will depend on the genotype of the F₁ plants. If they are heterozygous, the offspring will show a 1:1 ratio of dominant to recessive phenotypes, while a homozygous dominant would yield only dominant phenotypes.