Honors Genetics Problems

Honors Genetics Problems Directions: Answer the following questions on your own paper. Be sure to show all of your work.

Monohybrid Crosses 1. Two parents are each heterozygous for the recessive gene of albinism. When they have children, what is the probability the (a) none of the children will be normal, (b) all of the children will be normal, (c) 3 will be normal and one will be an albino.

2. Short hair is due to a dominant gene L in rabbits and long hair is due to a recessive allele l. A cross between a short haired female and a long haired male produced a litter of 1 long haired and 7 short haired bunnies. (a)What are the genotypes of the parents? (b) What phenotypic ratio was expected in the offspring generation? (c) How many of the 8 bunnies were expected to be long haired?

3. In guinea pigs, black coat B is dominant over white coat b. If a homozygous black coated male was mated with a homozygous white coated female, what would the genotype and phenotype of the F1 generation be? If two F1 offspring were mated, what would the genotypes and phenotypes of the F2 be?

4. In a certain animal, black fur, B, is dominant to white fur, b. Determine the expected genotypic and phenotypic ratios resulting from the following crosses: (a) homozygous black x white, (b) two heterozygous blacks, (c) heterozygous black x white.

Dihybid Crosses 5. T= tall pea plants which are dominant to t=short pea plants. S=smooth seeds which are dominant to s=wrinkled seeds. Cross a homozygous tall smooth plant with a short wrinkled plant. What are the genotypes and phenotypes of the F1 generation? Then cross two members of the F1 and give genotypes and phenotypes expected for the F2 generation.

6. In cattle H=hornless allele dominant to h=horned and B=black allele is dominant to b=red. Give all the possible genotypes and phenotypes expected in the following crosses: (a) horned red cow and a homozygous hornless, homozygous black bull, (b) horned red cow and a heterozygous hornless, heterozygous black bull, (c) heterozygous hornless, red cow and a horned, heterozygous black bull.

7. In sheep, M=fine wool which is dominant to m=mealy wool. W=white wool which is dominant to w=red wool. Cross a mealy red wooled sheep with a heterozygous fine, homozygous white wool sheep. Give the genotypes and phenotypes expected from their offspring.

Incomplete Dominance 8. In snapdragons, yellow flowers (Y) are not dominant to red flowers (R) and vice versa. They will blend to make a new color orange (RY). Complete the following crosses and give the genotypes and phenotypes of the offspring. (a) Cross a red flower with a yellow flower, (b) cross an orange flower with an orange flower, (c) cross an orange flower with a red flower.

Blood Type 9. A man’s maternal grandfather has type AB blood while all other grandparents are type O. What are the chances of the man being (a) type A, (b) type B, (c) type O, (d) type AB. 10. A woman with type A blood marries a man with type O blood. The wife’s father is type O. What is the probability that their expected child will be type O?

11. John has type O blood, his father is type B and his mother is type A. What are the genotypes of John’s parents?

12. One parent is homozygous for type A and the other parent has type O blood. What are all the possible blood types of their children?

13. A child has type O blood. What are all the possible genotypes of his parents?

14. If two newborn babies were accidentally mixed up in the hospital, there would be a question of which baby belonged to which parents. From the following blood types, determine which baby belongs to which parents. Then determine the genotype of each of the six people in the problem. Baby 1 type O Baby 2 type A Mrs. Brown type B Mr. Brown type AB Mrs. Smith type B Mr. Smith type B

Sex Linkage-Remember the alleles are carried on the X chromosome. Nothing is carried on the Y. 15. The normal vision allele would be XC and the color blindness allele would be Xc. Sam has normal color vision. His oldest sister is color blind and his younger sister has normal vision. What are the genotypes of his parents?

16. The disease where the blood does not clot is called hemophilia. It is a sex linked disorder. A man and his wife have 2 boys and 4 girls. One of the boys has hemophilia. The other boy and the girls do not. What are the genotypes of the parents?

17. John is color blind. His brother Bill and his sister Sue are not. John’s father has normal vision. Is John’s mother color blind? What are the genotypes of John’s parents and his sister?

18. A normal vision woman whose father was colorblind marries a normal vision man. They have two married daughters. The first daughter has 5 sons, all with normal vision. The second daughter has two normal daughters and a colorblind son. List the genotypes of all the above people.

19. Why is it not possible for a male to be heterozygous for colorblindness?

20. Why is it not possible for a male to be heterozygous for hemophilia?

21. There are about ten times as many colorblind men as colorblind women. Explain why?

22. If a woman who is not a carrier of the genes for hemophilia is married to a man who is a hemophiliac, what percentage of their male offspring could be expected to be hemophiliacs?