Codominance and Incomplete DominanceName: ______

CODOMINANCE

GenotypePhenotype

AA, AOType A

BB, BOType B

ABType AB

OOType O

And with respect to Rh factor, Rh+ is dominant, Rh- is recessive. So, an individual who is BO+- will have type B+ blood, and an individual who is AB-- would have type AB- blood.

1. Make one Punnett Square to figure out each of the following problems:

a. Mom is type O, Dad is type AB, b. Mom is type AB, dad is type AB.

What is the chance of having a type B kid?What is the chance of having an AB kid?

2. Make TWO Punnett Squares for each of the following problems:

a. Mom is type AB, dad is type B. b. Mom is type A, Dad is type O.

What is the chance of having a type B kid?What is the chance of having an O kid?

3. Make THREE Punnett Squares to solve each of the following problems:

a. Mom is type O+, dad is type O-. What is the chance of an O- kid?

b. Mom is AB-, Dad is O+. What is the chance of an A+ kid?

4. Use Punnett Squares to solve these problems.

a. What blood types can the children of a AB mom and a B dad have?

b. What blood types can the children of a B+ mom and an O- dad have?

c. Could a B+ mom and an A+ man have an O- child?

d. Could a child with A+ blood have an O- dad and an AB- mom?

e. Letitia and Carl’s baby, Elise, developed a liver problem when she was just a week old. The treatments cost hundreds of thousands of dollars, and Letitia and Carl did not have enough health insurance to cover the costs. Looking through the medical files, Carl noticed that his daughter was listed as being type 0 blood. He was surprised because he knew that he was type A and that his wife was type AB. Carl rechecked his wife’s medical records and his own before calling the police to report a baby-swapping crime. Was Carl right to suspect baby-swapping, or is his memory of blood type genetics a little hazy?

f. Shaken up by the news of a recent murder of a woman in the neighborhood where she works, Sharon was cautious going from the bus to the store where she worked. Emptying the trash from the weekend, she noticed some bloody rags. Her boss explained that his 10-year-old son had been in town for the weekend and had gotten a bloody nose when he tried to get a heavy box off a high shelf in the storage room. Sharon trusted her boss and needed her job badly, but still, after work she called the police to check up on the story. The police ran a blood test on the rags as well as on Sharon’s boss. The blood type on the rag was A and the boss’s blood type was O. Do the results back up his story, or not?

g. Carlos and Marie were sick with worry about their son, Miguel. Miguel was a freshman in college in a town a hundred miles away and had been missing for six days. When police found an abandoned car with blood spatters in it 30miles from campus, they feared the blood might be Miguel’s. They ran a blood test and called his parents. The blood from the car was A+. Carlos and Marie called their doctor to find out their own blood types and to find out if the blood was possibly Miguel’s. The doctor reported that Carlos had type A- and Marie had type O-. Should Carlos and Marie be worried or relived?

h. Christian’s father had left his mother when Christian was just two years old and his mom was still in high school. Since then, his mom had graduated from high school, gotten a business degree, and opened up a chain of agencies in the city. When she died in a car accident at age 34, she was worth 1.3 million dollars and Christian inherited all of it. Soon after, a man named Charlie appeared and said that he was Christian’s father. He said he had always wanted to be in Christian’s life, but he could not come near him as long as Christian’s mother was alive. Christian really enjoyed Charlie, and Charlie seemed to show no great interest in Christian’s money, but Christian wanted to know for sure. He asked Charlie to get a blood test. Charlie’s blood type came back as A+. Christian’s own blood type was B+. Should Christian tell Charlie “Get lost!”, “Glad to have you in my life, dad!”, or “I think we need a DNA test”?

INCOMPLETE DOMINANCE

1. A breed of chicken can have feathers on its legs that are dark brown, tan, or white. D codes for dark brown, W codes for white. Use Punnett Squares to answer the following:

a. Give phenotype probabilities for each of these crosses:

DD x DDDD x DW

DW x DWWW x WW

b. A farmer buys a rooster which the breeder claims is “true-breeding,” meaning that it should be homozygous. The rooster has dark brown feathers on its legs. Was the breeder telling the truth? Explain.

c. Chickens with tan feathers did especially well at the state fair last year, and the farmer would like to have more of them. Which would be the best hen to mate the dark brown-legged rooster with in order to get the most tan-legged chicks? A hen with dark brown feathers, a hen with tan feathers, or a hen with white feathers? Explain.

2. A flower has alleles for red color (R) and for white color (W). If this gene for flower color follows a pattern of incomplete dominance, what color would you expect a heterozygous flower to be?

3. Chinchillas homozygous for the F allele are white-bellied, those that are homozygous for the T allele are tan-bellied, and heterozygotes have cream bellies. Two chinchillas are crossed and produce many litters. Half of their young have white bellies, half have cream bellies, and they never produce a baby chinchilla with a tan belly. What were the genotypes of the parents? Use a Punnett Square to illustrate.

CODOMINANCE VS. INCOMPLETE DOMINANCE

State whether each of these situations is an example of codominance, incomplete dominance, or normal dominance.

1. A rabbit that is SS for coat pattern has stripes, a rabbit that is ss has spots, and a rabbit that is Ss has both stripes and spots. ______

2. Kangaroos with the Y allele all have normal tails, but kangaroos that are homozygous for the y allele have unusually short tails. ______

3. Tigers inherit claws that are either extremely twisted, mildly twisted, or not twisted at all. ______

4. Dogs with the K allele are afflicted with a neurodegenerative disorder, dogs without the allele are not. ______

5. In pigeons, the G allele codes for production of the enzyme A.L.A.T., and the J allele codes for production of the enzyme A.S.A.T. Heterozygous pigeons produce both A.L.A.T. and A.S.A.T. ______

6. Crossing a heterozygote with a heterozygote produces a 75% chance of offspring with the dominant version of a trait, and a 25% chance of offspring with a recessive version of a trait. ______

7. Crossing a heterozygote with a heterozygote produces 25% red flowers, 25% yellow flowers, and 50% orange flowers. ______