Alternate Patterns of Heredity

Traits Expressed by Multiple Genes A trait can be influenced by several genes. A trait can be influenced by several genes. The genes are scattered along chromosomes or even located on the same chromosome. The genes are scattered along chromosomes or even located on the same chromosome. Many combinations appear in offspring, for instance eye color, height, weight, skin or hair color. Many combinations appear in offspring, for instance eye color, height, weight, skin or hair color.

Incomplete Dominance Sometimes you can cross two different colored flowers and get offspring with a blending of the two. Sometimes you can cross two different colored flowers and get offspring with a blending of the two. Por ejemplo: When you cross a red flower with a white flower you end up with a pink flower. Por ejemplo: When you cross a red flower with a white flower you end up with a pink flower. This is called incomplete dominance. A displayed trait that is the intermediate between the two parents. This is called incomplete dominance. A displayed trait that is the intermediate between the two parents.

What About a mixture of the Two Sometimes you will see flowers that will show both colors of the parents. Sometimes you will see flowers that will show both colors of the parents. Codominance – When both dominant alleles are expressed at the same time. Codominance – When both dominant alleles are expressed at the same time. For example a flower with a mixture of both red & white petals. For example a flower with a mixture of both red & white petals.

Traits Controlled by Three or More Alleles Genes with three or more alleles are said to have multiple alleles. Genes with three or more alleles are said to have multiple alleles. For example… your blood type. For example… your blood type. There are three alleles for blood type There are three alleles for blood type IA, IB, iIA, IB, iIA, IB, iIA, IB, i  The possible phenotypes from this cross are A, AB, B, and O.

Lets Try It Lets say a person with AB blood crosses with a person with O type. What would a punnett square look like? Lets say a person with AB blood crosses with a person with O type. What would a punnett square look like? What are the phenotypes of the children? What are the phenotypes of the children?

Do your own Perform a cross between a parent who is homozygous for blood type A and a parent who is homozygous for blood type B Perform a cross between a parent who is homozygous for blood type A and a parent who is homozygous for blood type B What is the percentage of the phenotype? What is the percentage of the phenotype?