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Name:__________________________________ Review Guide Genetics Review of Monohybrid Crosses 1. The gene for freckles (F) is dominant over the gene for no freckles (f). Using this information, show a cross between one person who is heterozygous for the trait and another who is homozygous for the trait. a. All possible genotypes ______________________ b. Genotypic ratio ____________________________ c. All possible phenotypes _____________________ d. Phenotypic ratio ____________________________ e. What is the probability of the two individuals having a child with freckles? __________________________ 2. Now, cross two people who are heterozygous with the alleles mentioned in question 1. a. All possible genotypes _______________________ b. Genotypic ratio ____________________________ c. All possible phenotypes ______________________ d. Phenotypic ratio ____________________________ e. What is the probability that a child will be born with no freckles? ___________________________________ 3. Consider the following cross: yellow pea plants x green pea plants all yellow pea plants most yellow pea plants and some green plants a. Which color is recessive, green or yellow? _________ b. If the F1 generation has 4 plants, how may should be yellow? (Give an actual number, not a percentage.) ____________________ c. If the F1 generation has 80 plants, how many should be yellow? (Give an actual number, not a percentage.) 4. You observe, among a group of offspring, that there are 74 purple flowers and 68 white flowers. (P = purple, p = white) Give the phenotypic ratio of the offspring ____________________ Give the most likely parental genotypes _____________________ Give the most likely parental phenotypes ____________________ 5. You observe, among a group of puppies, that there are 6 with dark coats and 2 with light coats. (D = dark and d = light) Give the phenotypic ratio of the offspring ____________________ Give the most likely parental genotypes _____________________ Give the most likely parental phenotypes ____________________ 6. In sesame plants, the one-pod condition (P) is dominant to the three-pod condition (p), and normal leaf (L) is dominant to the wrinkled leaf (l). The offspring produced in one cross yield 223 one-pod normal, 72 one-pod wrinkled, 76 three-pod normal, 27 three-pod wrinkled. Give the phenotypic ratio of the offspring ____________________ Give the most likely parental genotypes _____________________ Give the most likely parental phenotypes ____________________ 7. In a fictitious organism called a “tribble,” red color is dominant over white. A normal red tribble is crossed with one that does not have the color. The offspring that result are 8 tribbles, all of which born with red color. Use this information to provide the most probable parental genotypes. ____________________________________ 8. In dogs, spots on body (T) are dominant over no spots (t). Dark eyes (D) are dominant over blue eyes (d). Two blue eyed dogs are crossed to produce 10 puppies with spots and 11 puppies with no spots. What is the most probable genotype for the parents for eyes and spots? ____________________________________ 9. Complete the following 4x4 Punnet square, showing all the possibilities of gametes that can result from these two heterozygote parents. After you complete the square, then determine the phenotypic ratio at the bottom. (P = purple, p = white, S = smooth, s = wrinkled) 10. In the previous problem, the gametes that resulted from the parent (PpSs) included PS, Ps, pS, and ps. Determine the gametes that would result from each of the following genotypes for possible parents: a. PpGg _________________________________ b. ppGg _________________________________ c. Llbb__________________________________ d. aagg___________________________________ 11. Show a cross between the following dogs, making sure to construct a Punnet square in the space provided. (D= dark eyes, d= blue eyes; W= wire hair, w= shaggy hair) DdWw x DDWw a. Possible phenotypes ___________________________ b. Phenotypic ratio ______________________________ 12. A man and woman are going to have children. The woman is homozygous for type A and the man is homozygous for type B. Show a Punnett square that illustrates this cross and then answer the following. a. Possible genotypes ___________________________ b. Genotypic ratio ______________________________ c. Possible phenotypes __________________________ d. Phenotypic ratio ______________________________ e. Chance of having a child with O blood ____________ 13. In a case in Spokane, Washington, a young woman accused a soldier of being the father of her child. The soldier, of course, denied it. The soldier’s lawyer demanded that blood types be taken to prove the innocence of his client. The following were obtained: Alleged father- Type O. Mother- Type A. Child- Type AB. The court found the soldier guilty on the basis of the woman’s remarkable memory for dates and details that apparently eliminated all other possible fathers. a. Possible genotypes for these people _______________________________ b. Do you agree with the court’s decision? Why or why not? 14. Horses have different alleles for body color, but two of these alleles include the chestnut (dark brown) allele and a diluting (pale cream) allele (often incorrectly called ‘albino’), which display incomplete dominance. A horse heterozygote for these two alleles is a palomino. (Let C= chestnut, P= pale) Illustrate a cross between two palominos. a. In the space provided on the left, draw a Punnett square to illustrate the cross. b. Genotypic ratio __________________________ c. Phenotypic ratio _________________________ d. Probability that the offspring will be a pale horse? _____________________________ e. Draw a Punnet square on the left to illustrate the cross between a palomino and a chestnut horse.