In a cross between two heterozygous individuals, what is the expected phenotypic ratio?

In a cross between two heterozygous individuals, the expected phenotypic ratio is 3:1. This outcome can be explained using principles of Mendelian genetics.

When two heterozygous individuals (for example, both with genotype Aa, where "A" represents the dominant allele and "a" represents the recessive allele) are crossed, the possible gametes produced from each parent are A and a. Therefore, when these gametes combine during fertilization, the resulting genotypes of the offspring can be AA, Aa, Aa, and aa.

Genotypically, this produces the following results:

• 1 AA

• 2 Aa

• 1 aa

In terms of phenotypes, assuming A is dominant and a is recessive, both AA and Aa individuals will express the dominant phenotype, while only the aa individual will express the recessive phenotype. Therefore, the phenotypic breakdown is:

• 3 (AA and Aa) exhibiting the dominant phenotype

• 1 (aa) exhibiting the recessive phenotype

This ratio of 3 dominant : 1 recessive directly reflects the expected phenotypic ratio resulting from this genetic cross.