AP BIOLOGY

Detailed explanation-1: -The number of phenotypes produced for a given trait depends on how many genes control the trait. Height in humans is an example of a single-gene trait . Each gene of a polygenic trait often has two or more phenotypes . A single polygenic trait often has many possible genotypes .

Detailed explanation-2: -A polygenic trait is a characteristic, such as height or skin color, that is influenced by two or more genes. Because multiple genes are involved, polygenic traits do not follow the patterns of Mendelian inheritance. Many polygenic traits are also influenced by the environment and are called multifactorial.

Detailed explanation-3: -The number of phenotypes possible is determined by the dominance relationships between the three alleles.

Detailed explanation-4: -Genes are contained in chromosomes, which are in the cell nucleus. A chromosome contains hundreds to thousands of genes. Every normal human cell contains 23 pairs of chromosomes, for a total of 46 chromosomes. A trait is any gene-determined characteristic and is often determined by more than one gene.

Detailed explanation-5: -Traits that show a large number of phenotypes are usually controlled by many genes. With multiple genes and two or more alleles for each gene, there are many possible combinations of alleles and phenotypes.