GENETICS QUESTIONS 2

1. George has Royal hemophilia and marries his mother's sister's daughter Patricia. His maternal grandfather also has hemophilia. George and Patricia have 5 children: 2 daughters are normal, and 2 sons and 1 daughter develop hemophilia. Draw the pedigree.

2. A woman is married for a 2nd time. Her first husband was blood type A and her son by that marriage was type O. Her new husband is type B and their child is type AB. What is the woman's blood group and genotype?

3. A normally pigmented man (dominant) marries an albino woman (recessive). They have 3 children, one of whom is an albino. What is the genotype of the man?

4. Four babies were born within minutes of each other in a large hospital, when a sudden explosion occurs. All four babies are found alive among the rubble, but none had yet been given their identity bracelets. The babies prove to be of four different blood groups: A, B, AB, O. The four pairs of parents have the following blood groups: A & B, O & O, AB & O, and B & B. Match parents to babies.

5. In sesame, the one-pod condition (P) is dominant to the three-pod condition (p), and normal leaf (L) is dominant over wrinkled leaf (l). The two characters are inherited independently. Determine the genotypes and phenotypes of the two plants which produce the following progeny: 318 one-pod normal, 98 one-pod wrinkled, 323 three-pod normal and 104 three-pod wrinkled.

6. Flower position, stem length, and seed shape were three traits that were studied by Mendel. Each is controlled by an independently assorting gene. If a plant that is heterozygous for all three traits was allowed to self-fertilize, what proportion of the offspring would be expected to show all three dominant phenotypes?

7. In horses coat color is dependent upon genes as follows: A_B_ results in bay, aaB_ in black, A_bb in chestnut, aabb in liver. In addition, palimino is derived by Dd with chestnut. A palimono stallion (DdAAbb) is crossed with a palimino mare (DdAAbb). What percent of the offspring will be palimino?

8. The dominant gene (G) produces green hair in mermaids and the recessive gene (g) produces blue hair. Webbed fingers are due to the dominant gene (F) and normal fingers are recessive (f). A mermaid who was heterozygous for hair color and who had normal fingers had a father with blue hair and webbed fingers and a mother with green hair and webbed fingers. What are the genotypes of all individuals (as completely as possible)?

9. In cucumbers normal leaves (N) are dominant to curled leaves (n) and elongated fruit (L) is dominant to spherical fruit and these genes are linked on the same chromosome. If a pure-breeding normal-leaved, elongated fruit cucumber is crossed with a curled-leaved, spherical fruit cucumber, what will be the phenotype of the F1? the phenotypic ratio of the F2?

10. A certain man has the genotype AaBb; genes A and B are on one chromosome and a and b are on its homologue. List the gametes that could be formed with crossing over and with no crossing over.

11. A normal woman whose father was a hemophiliac marries a normal man. What are the chances of hemophilia occurring in their children?

12. In cats yellow is due to gene B and black to its allele b. These genes are located on the X chromosome (sex-linked). The heterozygous results in calico (tortoise shell). What kinds of offspring (sex & color) are expected from the cross: black male & calico female? Most calico males are sterile, why?

13. The ABO blood system has been employed to settle cases of disputed paternity. Suppose, as an expert in genetics, you are called to testify in a case where the mother is type A, the child is type O and the alleged father is type B. How would you respond to the following statements of the attornies:
a. "Since the mother has type A, the type O of the child must have come from the father and since my client is type B, he obviously could not have fatered the child." Made by the attorney of the alleged father.
b. "Further tests revealed that this man is heterozygous and therefore he must be the father." Made by the mother's attorney.

14. The rare trait of ocular albinism (almost complete absence of eye pigment) is inherited as a sex-linked recessive. A man with ocular albinism marries a woman who neither has this trait nor is a carrier. What would you predict about their offspring concerning this trait?

15. In a cross AABBCC and aabbcc (P generation), what would be the frequency of AAbbCc in the F­2 (assuming no linkage)?

16. Consider two linked autosomal genes. The dominant allele C of the first gene causes cataracts of the eye, whereas its recessive allele produces normal eyes. The dominant allele P causes polydactyly (an extra finger) whereas its allele (p) produces a normal number of fingers. A man with cataracts and normal fingers marries a woman with polydactyly and normal eyes. Their son has both polydactyly and cataracts and he marries a woman with neither trait. What is the probability that their first child will have cataracts and polydactyly?

17. Pooh had a colony of tiggers whose stripes ran across the body. His American buddy Yogi, sent him a tiggerwhose stripes ran lengthwise. When Pooh crossed Yogi's tigger with one of his own, he obtained plaid tiggers. Interbreeding among the plaid tiggers produced litters with a majority of plaid tiggers but also some crosswise and lengthwise striped tiggers. Diagram these crosses and explain the results.

18. The weight of the fruit of one variety of squashes is determined by three pairs of genes: AABBCC produces 6 lb squashes and aabbcc produces 3 lb squashes. Each dominant allele adds 1/2 lb tothe base weight (3 lb). If a pure breeding line that produced 6 lb squashes was crossed with a pure breeding line that produced 3 lb squashes, what would be the phenotypic ratio of the F1 and the F­­2?

19. In snapdragons tallness (T) is dominant to dwarfness (t). Red flowers are produced by RR and white flowers by rr but the heterozygous Rr is pink. A dwarf red snapdragon is crossed to a homozygous tall plant with white flowers. What is the phenotypic ratio of the F­1? the F2?