AP BIOLOGY

Detailed explanation-1: -A dominant allele is denoted by a capital letter (A versus a). Since each parent provides one allele, the possible combinations are: AA, Aa, and aa. Offspring whose genotype is either AA or Aa will have the dominant trait expressed phenotypically, while aa individuals express the recessive trait.

Detailed explanation-2: -If there are two alleles in a population at locus A (A and a), then the possible genotypes in that population are AA, Aa, and aa. Individuals with genotypes AA and aa are homozygotes (i.e., they have two copies of the same allele).

Detailed explanation-3: -That can be either AA or aa, homozygous dominant or homozygous recessive. 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: -For this example, let us define “A” as being the dominant normal allele and “a” as the recessive abnormal one that is responsible for cystic fibrosis. As carriers, you and your mate are both heterozygous (Aa). This disease only afflicts those who are homozygous recessive (aa).

Detailed explanation-5: -An organism with two dominant alleles for a trait is said to have a homozygous dominant genotype. Using the eye color example, this genotype is written BB. An organism with one dominant allele and one recessive allele is said to have a heterozygous genotype. In our example, this genotype is written Bb.