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Punnet Square-Pedigree Short Answer One sex-linked trait occurring on the X chromosome is color blindness (XC). Study the pedigree below that shows the occurrence of color blindness in three generations of a family. Use the information below to help answer the following questions. X=X chromosome Y=Y chromosome C=normal vision C=color-blind trait 1. What is the genotype of the first generation female, person 4? ____________ 2. What is the probability in percent of person 6 passing on the color-blind trait? ______ % 3. What is the genotype of the first generation male, person 5? __________ 4. Person 5 is color-blind. However, his sons do not have this condition. What accounts for this? 5. What is the probability in percent of person 7 passing on the color-blind trait? ________ % Skill: Observing and Inferring Fur length is an inherited trait in guinea pigs. Short fur is dominant (F) and long fur is recessive (f). 6. What letters would be used to represent the genotype of these parents? ___________ 7. From your study of Mendel?s experiments, infer how two parents with short fur could have offspring with long fur. 8. Describe the phenotype of these parents. 9. Study the genetics problems below. Complete the Punnett squares by writing the parent genotypes in the correct place and determining the offspring genotypes. Then, describe each phenotype. 1. Dominant: chin cleft (C) 2. Dominant: dimples (D) Recessive: no cleft (c) Recessive: no dimples (d) Parents: CC ? cc Parents: Dd ? D 3. phenotype 1: _______________________________________ 4. phenotype 2: _______________________________________ 10. Complete the Punnett square by identifying the parental genotypes in the correct places and determining the possible genotypes of the offspring. Dominant gene: curly hair (H) Recessive gene: straight hair (h) Parents: Hh ? hh What are the genotypes and phenotypes of the offspring? Genotypes ____________ and _____________ Phenotypes ____________ and _____________ Problem 11. Write a pedigree for a family (parents and four children) in which one girl and one boy are color-blind while one boy and one girl are not. 12. If two people are heterozygous for cystic fibrosis, what are the chances that their children will have the disease? 13. Suppose you crossed a heterozygous yellow pea plant (Yy) with a homozygous green pea plant (yy). What are the possible genotypes and phenotypes of the offspring? Use the Punnett square in Figure 11-1 to compute your answers. Figure 11-1 Possible genotypes ___________________ and ___________________ Possible phenotypes ___________________ and ___________________ 14. The pedigree shown in Figure 11-2 shows the inheritance pattern in one family for color-blindness. How is this disease inherited? Figure 11-2 Multiple Choice Identify the choice that best completes the statement or answers the question. ____ 15. A Punnett square shows you all the ways in which _____ can combine. 1 sperm 3 alleles 2 eggs 4 colors ____ 16. In a Punnett square, a capital letter stands for a _____ allele. 1 dominant 3 homozygous 2 heterozygous 4 recessive ____ 17. Of the following, which represents a homozygous recessive genotype? 1 TTT 3 Tt 2 tt 4 TT Gr8-Ch5-PunnetSquare-Pedigree-Test2 Answer Section SHORT ANSWER 1. ANS: X X PTS: 1 2. ANS: 0% PTS: 1 3. ANS: X Y PTS: 1 4. ANS: Sons inherit on the Y chromosome from their father PTS: 1 5. ANS: 50% PTS: 1 6. ANS: Ff PTS: 1 7. ANS: In Mendel?s tall and short plants, the first generation produced showed all offspring with the dominant tall trait, but when seeds from those plants produced offspring, some short plants reappeared because those seeds carried the recessive factor. Both guinea pig parents must carry the recessive factor to have offspring showing the recessive trait. PTS: 1 8. ANS: They have short fur. PTS: 1 9. ANS: 3. all have chin cleft 4. 3 with dimples, 1 without PTS: 1 10. ANS: Hh, curly hair; hh, straight hair PTS: 1 PROBLEM 11. ANS: The pedigree should show that the father is color-blind (XcY) the mother is a carrier (XXc), one boy and one girl are color-blind (XcY, XcXc), one girl is a carrier (XXc), and one boy is normal (XY). PTS: 1 DIF: A OBJ: 8/2 STA: LE 2.2c LOC: NYC.1.h 12. ANS: The chances are one in four that their children will inherit both recessive genes and have cystic fibrosis. PTS: 1 DIF: A OBJ: 7/2 STA: LE 2.2a LOC: NYC.1.g 13. ANS: possible genotypes: Yy, yy; possible phenotypes: yellow, green PTS: 1 DIF: A OBJ: 3/1 STA: LE 2.2c LOC: NYC.1.h 14. ANS: The disease is sex-linked and inherited on the X chromosome. The mother is a carrier; the son has the disease; one daughter is a carrier; of the grandchildren, one girl is a carrier and one boy has the disease. PTS: 1 DIF: A OBJ: 8/2 STA: LE 2.2c LOC: NYC.1.h MULTIPLE CHOICE 15. ANS: 3 PTS: 1 DIF: B OBJ: 3/1 STA: LE 2.2c LOC: NYC.1.h 16. ANS: 1 PTS: 1 DIF: B OBJ: 3/1 STA: LE 2.2c LOC: NYC.1.h 17. ANS: 2 PTS: 1 DIF: B OBJ: 3/1 STA: LE 2.2b LOC: NYC.1.g ................
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