Lecture 6 - Codominance and Incomplete Dominance

Codominance

two different alleles for a gene are both expressed in the heterozygotes

What is an example of codominance in humans?

blood type. So the alleles I^A and I^B results in blood type AB (codominant)

Partial or incomplete dominance

essentially showing the blending theory (e.g. red and white flower offspring are pink)

What is the underlying molecular biology of partial or incomplete dominance?

Essentially the dominant allele (“R“) will encode for production of the red pigment. So RR will produce more red pigment than Rr. Therefore, Rr will give the “intermediate“ phenotype.

What could be the genotypes of blood type A? How about the antibodies made?

With the genotype of I^AI^A or I^AI^O, the antibodies made are Anti-B

How do we determine the probability that two independent events will BOTH happen?

multiply the probabilities of the individual events

How do we determine the probability of an event that can occur in two or more different ways?

find the sum of the individual probabilities of those ways.

Genetic interaction

the idea that several genes influence a particular characteristic

Epistasis

occur when the alleles of one gene cover up or alter the expression of alleles of another gene (e.g. coat color in mice)

What is 2nd form of epistasis?

two genes that are mutually dependent - the expression of each depends on the alleles of the other - complementary genes