Complex Patterns
By: raymone fuller
Multiple alleles
Examples: Two human examples of multiple-allele genes are the gene of the ABO blood group system, and the human-leukocyte-associated antigen genes. The ABO system in humans is controlled by three alleles, usually referred to as IA, IB, and IO (the "I" stands for isohaemagglutinin).
Incomplete dominance
Incomplete dominance refers to a genetic situation in which one allele does not completely dominate another allele, and therefore results in a new phenotype.
Example1:
A snapdragon flower that is pink as a result of cross-pollination between a red flower and a white flower when neither the white or the red alleles are dominant.- Example2:
- A brown fur coat on a rabbit as a result of one rabbit's red allele and one rabbit's white allele not dominating.
Codominance
Example1: Examples of codominance include a person with type AB blood, which means that both the A allele and the B allele are equally expressed
Example2: If a black cat and tan cat mate, the kitten will have both black fur and tan fur.
If a dog with white fur and a dog with black fur mate, they produce a dog with both white and black fur.
Polygenic traits
Example1:
Humans can be many different sizes. Height is a polygenic trait, controlled by at least three genes with six alleles. If you are dominant for all of the alleles for height, then you will be very tall. There is also a wide range of skin color across people.