1 / 14

Incomplete dominance Codominance Multiple alleles

Incomplete dominance Codominance Multiple alleles. Ch. 10.3 (p. 215-216). Incomplete dominance. This is a case where neither of the 2 alleles is totally dominant over the other So instead of having 2 phenotypes…we see an appearance of a 3 rd phenotype

mirra
Download Presentation

Incomplete dominance Codominance Multiple alleles

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Incomplete dominanceCodominanceMultiple alleles Ch. 10.3 (p. 215-216)

  2. Incomplete dominance • This is a case where neither of the 2 alleles is totally dominant over the other • So instead of having 2 phenotypes…we see an appearance of a 3rd phenotype • In dominant/recessive cases, AA and Aa showed the dominant phenotype • In incomplete dominance, Aa will show an intermediate of the other 2 phenotypes

  3. Example of incomplete dominance • Snapdragons Red x White (P1) All Pink (F1)

  4. Example con’t • All F1 offspring were heterozygous • Let’s take 2 F1 individuals to make an F2 generation Pink x Pink Red, Pink, and White

  5. Using alleles (letters) for incomplete dominance • Since there isn’t a recessive gene here, we WILLNOT use a lower case letter • Instead we use… R = Red R’ = White • So our possible genotypes and phenotypes are: RR = Red RR’ = Pink R’R’ = White

  6. RR x R’R’ (P1) All R R’ (F1) RR’ x RR’ 1RR: 2RR’: 1R’R’ *Also our phenotypic ratio is: 1 Red: 2 Pink: 1 White The example written in alleles (letters)

  7. Codominance • This is a case where neither of the 2 alleles is totally dominant over the other, but we can still see each phenotype product individually (they’re not blended) • So again, we’ll see 3 phenotypes instead of 2…the heterozygous will show a combination of the other 2

  8. Example of codominance • Chickens with checkered feathers: Black x White(P1) All checkered (F1) Written in alleles as: BB x B’B’(P1) All BB’ (F1)

  9. Example con’t • Taking it to the F2: BB’ x BB’ 1BB: 2BB’: 1B’B’ Phenotypic ratio: 1 Black: 2 Checkered: 1White

  10. Multiple Alleles • For some traits, more than 2 alleles exist in the population (each individual still only has 2 alleles for that trait) • Having more than 2 alleles increases the possible genotypes and phenotypes for the trait

  11. Example of multiple alleles • Blood type for humans • 3 alleles: IA = A IB = B i = O • IA and IB are codominant to each other • IA and IB are both dominant over i

  12. Blood Types

  13. Example multiple allele problem • A person homozygous for Type A marries a person with Type O. What are the possible outcomes of bloodtypes for their children?

More Related