Incomplete Dominance and Codominance

What is codominance?• When two alleles are BOTH expressed togetherExample: blood type– Blood type A = blood cells with A proteins– Blood type B = blood cells with B proteins– Blood type AB = blood cells with A and B proteins

Processing Piece:• Write “incomplete dominance.” Circle “co” and

write “together.”• Draw a picture to illustrate codominance. Example: Different blood types Example: A flower with red and white spots

What is incomplete dominance?• Two alleles are blended to produce a “blended

phenotype”Example: color in snapdragon flowers– WW = white– WR = pink– RR = Red

Processing Piece:

• Draw a picture to illustrate incomplete dominance. Example: White, red, and pink flowers

Sample Questions 1 and 2:Cow traits:BB = black BW = black and white WW = white1) Is this an example of incomplete dominance or

codominance?2) Two black and white cows are crossed. What are

possible phenotypes, and their %’s, for the offspring? (Draw a Punnet Square.)

Sample Questions 3 and 4:Cow traits:BB = black BW = grey WW = white3) Is this an example of incomplete dominance or codominance?4) A black cow and a grey cow are crossed. What are possible phenotypes, and their %’s, for the offspring? (Draw a Punnet Square.)

Sample Questions 5 and 6:Human traits:DD = fatal Dd = dwarfism dd = normal5) Is this an example of incomplete dominance or

codominance?6) A man of normal height marries a woman who is a

dwarf. What are possible phenotypes, and their %’s, for their kids? (Draw a Punnet Square.)

Exit TicketLabel each of the following as codominance or “incomplete dominance.”1) Blood type A x Blood Type B Blood Type AB2) Red flower x White flower Pink flower3) Red flower x White flower Red & White flower