Codominance: Understanding the Phenotypic Effects of Two Alleles for a Gene

The video explains codominance, where two alleles affect the phenotype equally. It provides examples such as ABO blood groups in humans and feather color in hens. In ABO blood groups, alleles IA and IB are codominant, while IO is recessive. In hens, alleles for black and white feathers are codominant, resulting in speckled feathers. The video concludes with a summary of these concepts.

What is codominance?

• When alleles do not affect the phenotype

• When alleles are recessive

• When two alleles for a gene both affect the phenotype

• When one allele is completely dominant over the other

Which alleles are involved in determining the ABO blood group?

• IA, IB, IC

• IA, IC, IO

• IB, IC, IO

• IA, IB, IO

What blood type results from having one IA and one IB allele?

• Type AB

• Type B

• Type A

• Type O

In hens, what feather color results from having one B and one W allele?

• Speckled feathers

• No feathers

• All white feathers

• All black feathers

What does it mean when alleles are described as codominant?

• One allele is stronger than the other

• Both alleles are equally expressed

• Neither allele is expressed

• Both alleles are recessive