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HEREDITY WORKSHEET Name: MONOHYBRID CROSSES WITH DOMINANT TRAITS 1. The table below indicates dominant and recessive traits in corn plants. Refer to this information for questions 1 – 7. Dominant Recessive Tall (T) Short (t) Green (G) Albino (g) 2. In corn plants, plant height is determined by one gene with two alleles. a) How many alleles that control the trait for height are present in each cell nucleus of a corn plant? b) How many alleles that control the trait for height are present in each gamete (sperm or egg cell) of a corn plant? 3. What are the genotypes of corn plants that are… a) Homozygous tall: b) Heterozygous tall: c) Dwarf: 4. What are the genotypes of possible gametes of corn plants that are… a) Homozygous tall: b) Heterozygous tall: c) Dwarf: 5. What is the predicted phenotype ratio in the progeny of a cross between two corn plants that are both heterozygous tall? a)
b)
c)
d)
Parent phenotypes: Parent genotypes: Gametes: Punnett Square: X X X ____________ ____________ e) What is the ratio of genotypes in this mating? f) What is the ratio of phenotypes in this mating? 6. Using the same method as above, determine the expected progeny in a cross between a heterozygous tall corn plant and a dwarf corn plant. a) Parent phenotypes: X b) Parent genotypes: X c) Gametes: X d) Punnett Square: ____________ ____________ e) What is the ratio of genotypes in this mating? f) What is the ratio of phenotypes in this mating? 7. Refer to the table on the first page. Determine the expected progeny of a cross between a heterozygous green corn plant and an albino corn plant. a) Parent phenotypes: X b) Parent genotypes: X c) Gametes: X d) Punnett Square: ____________ ____________ g) What is the ratio of genotypes in this mating? a) What is the ratio of phenotypes in this mating? 8. The table below lists dominant and recessive traits in pea plants. Refer to this information for questions 9 – 11, and question 22. Use the extra space on the next page in case you need to sketch out Punnett squares or make notes. Dominant Recessive Purple (P) White (p) Round (R) Wrinkled (r) Yellow seed (G) Green seed (g) 9. Refer to the table above. What are the possible genotypes of parent pea plants in crosses that yield the following ratios: Parent Genotypes a) 3 round seeds : 1 wrinkled seed b) all white flowers c) all purple flowers (3 possibilities) X X X X X X d) 1 round seed : 1 wrinkled seed 10. Is it possible to observe differences between homozygous and heterozygous individuals that both possess the dominant allele? 11. To determine the genotype of a tall pea plant by using a test cross, it should be crossed with a pea plant. In this test cross, what would the genotype of the tall pea plant be if… a) All the progeny are tall: b) Half the progeny are tall: DOMINANT/RECESSIVE TRAITS DETERMINED BY A SINGLE GENE 12. The following table lists some human traits that are determined by a simple dominant/recessive mode of inheritance. Record your phenotypes and the frequency of the phenotypes among members of your class. Trait Phenotype Handedness Right-‐handed* Left-‐handed Ear lobes Free* Attached Freckled* Non-‐freckled Widow’s peak* Straight Little finger Bent* Straight Tongue roll Yes* No Rh factor Rh+* Rh-‐ Freckles Hairline Your phenotype Number in class with Phenotype * Indicates a dominant trait. a) For each trait, is the dominant phenotype always more abundant among class members? b) Assume your class is representative of the general population. What can you conclude about the relationship between dominant and recessive phenotypes and their frequencies in the population? 13. Newlyweds Bill and Sue are non-‐freckled, but they each have one parent with freckles. They wonder about the probability of their children having freckles. What would you tell them? 14. Mary has freckles, but her husband Dick does not. Mary’s father has freckles, but her mother does not. What is the probability that Mary and Dick will have a freckled child? INCOMPLETE DOMINANCE AND CODOMINANCE 15. Contrast the inheritance patterns of incomplete dominance and codominance. a) Incomplete dominance: b) Codominance: 16. What are the genotype and phenotype ratios of a cross between two snapdragons with pink flowers (in snapdragons, red color is incompletely dominant with white). a) Genotype ratio: b) Phenotype ratio: 17. Sickle-‐cell anemia also exhibits incomplete dominance with the allele for normal blood cells. What is the probability that parents who are both heterozygous for sickle-‐cell hemoglobin would have a child with at least some sickle-‐cells? ABO BLOOD TYPES AND Rh FACTOR 18. Rh blood type is determined by two alleles. The allele for Rh+ blood is dominant, and the allele for Rh-‐ blood is recessive. a) Linda is Rh-‐, and is pregnant. Her husband Tom is Rh+, as are both of his parents. What is Linda’s genotype? b) What are the two possible genotypes for Tom? c) What is the probability of Linda and Tom’s baby being Rh-‐ if… Tom is homozygous for Rh+ blood? i.
Tom is heterozygous for Rh+ blood? 19. True or false? ii.
a)
b)
c)
d)
A type O child may have two type A parents: A type O child may have one type AB parent: A type B child may have two type AB parents: A type AB child may have on type O parent: 20. Ann (type A, Rh+ blood) is suing Joe (type AB, Rh-‐ blood) for child support. She claims that he is the father of her child (type B, Rh+ blood). a) From this information, is it possible that Joe is the father of Ann’s child? b) What blood type(s) would Joe have to possess to prove that he is NOT the father of Ann’s child? 21. Alleles for type A or B blood (dominant) are indicated with an A or B. The allele for type O blood (recessive) is indicated with an O. What is the expected genotype and phenotype ratios of these matings: a) AB X OO Genotype ratio: Phenotype ratio: b) AO X BO Genotype ratio: Phenotype ratio: DIHYBRID CROSSES WITH DOMINANCE 22. Determine the phenotype ratio in the progeny of a cross between two yellow-‐round, dihybrid pea plants. Refer to the table of dominant/recessive traits for pea plants. a) Parent phenotypes: X b) Parent genotypes: X c) Gametes: X d) Punnett Square: ________ ________ _______ ________ 23. List the possible gametes of a dihybrid organism with a genotype of AaBb. a) Possible gametes: 24. If two tall-‐green, dihybrid corn plants were crossed, each with a genotype of TtGg, what would be the expected phenotype ratio in the progeny? Refer to the table on the first page. Tall-‐green: Dwarf-‐Green: Tall-‐albino: Dwarf-‐albino: SEX-‐LINKED GENES 25. Why are more males color-‐blind than females? 26. The allele for color-‐blindness is indicated here as: XC. Determine the expected phenotype ratio of children from these matings: a) Normal female (XX) X color-‐blind male (XCY): C
b) Carrier female (XX ) X normal male (XY): PEDIGREE ANALYSIS 27. Refer to the symbols below and examine the pedigrees (family trees) below. Determine whether the inherited trait (n or ●) is dominant, recessive or sex-‐linked recessive. a) b) c)