AP BIOLOGY

Detailed explanation-1: -A cross between two pure breeding dominant (AA) and recessive (aa) parents give all dominant progeny. Homozygous dominant (AA) and heterozygous dominant (Aa) parents give homozygous and heterozygous dominant progeny in 1:1 ratio. Thus, the correct answer is option B.

Detailed explanation-2: -A monohybrid cross between a parent that is homozygous dominant and a parent that is homozygous recessive for a particular trait produces offspring that are all heterozygous for that trait. These individuals have two different alleles for that trait.

Detailed explanation-3: -An individual who is homozygous dominant for a particular gene will have two dominant “A” alleles for that gene. An individual who is homozygous recessive will have the “aa” genotype, two recessive “a” alleles.

Detailed explanation-4: -If we cross two heterozygous individuals (Aa), then the percentage of offsprings with recessive phenotype will be: Aa x Aa = AA Aa Aa aa, so recessive phenotypes would be 1/4 = 25%.