AP BIOLOGY

Detailed explanation-1: -With one gene controlling a trait we have three possible genotypes, AA, Aa and aa and depending on the allelic interactions (dominance or incomplete dominance) we can have two or three phenotypes.

Detailed explanation-2: -Number of genotypes for a given number of alleles Given n alleles at a locus, the number genotypes possible is the sum of the integers between 1 and n: With 2 alleles, the number of genotypes is 1 + 2 = 3.

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: -Traits controlled by a single gene with more than two alleles are called multiple allele traits.

Detailed explanation-5: -If both alleles are dominant, it is called codominance?. The resulting characteristic is due to both alleles being expressed equally. An example of this is the blood group AB which is the result of codominance of the A and B dominant alleles.