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: -Homozygous dominant denoted by two uppercase letters such as AA contain two copies of the alleles and diploid cells encoding for the dominant phenotype. In this case, the dominant trait is guaranteed to be expressed. An example of a homozygous dominant trait is brown eyes or freckles.

Detailed explanation-3: -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.

Detailed explanation-4: -As carriers, you and your mate are both heterozygous (Aa). This disease only afflicts those who are homozygous recessive (aa).

Detailed explanation-5: -If the dominant allele is labeled as “A” and the recessive allele, “a”, three different genotypes are possible: “AA”, “aa”, and “Aa”. The term “homozygous” is used to describe the pairs “AA” and “aa” because the alleles in the pair are the same, i.e. both dominant or both recessive.