Genetics Review Questions ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ 1. What did Gregor Mendel do to study different characteristics in his genetics experiments? 2. In Mendel’s experiments, what proportion of the plants in the F2 generation had a trait that had been absent in the F1 generation? 3. Factors that control traits are called 4. Scientists call an organism that has two different alleles for a trait a 5. What does the notation TT mean to geneticists? 6. What does the notation Tt mean to geneticists? 7. What is probability? 8. What did Mendel predict was the probability of producing a tall plant from a genetic cross of two hybrid tall plants? 9. What does a Punnett square show? 10. If a homozygous black guinea pig (BB) is crossed with a homozygous white guinea pig (bb), what is the probability that an offspring will have black fur? 11. An organism’s physical appearance is its 12. What does codominance mean in genetics? 13. What happens during meiosis? 14. When sex cells combine to produce offspring, each sex cell will contribute 15. Which term refers to physical characteristics that are studied in genetics? 16. The different forms of a gene are called 17. What does the notation tt mean to geneticists? 18. An organism’s genotype is its 19. An organism that has two identical alleles for a trait is 20. A heterozygous organism has 21. Which of these traits is controlled by a gene with multiple alleles? 22. What are multiple alleles? 23. Why does height in humans have such a wide variety of phenotypes? 24. What controls variations in skin color among humans? 25. Which of these human traits is altered by variations in environment? 26. What factors can affect a person’s height? 27. Which combination of sex chromosomes results in a male human being? 28. Why are sex-linked traits more common in males than in females? 29. How does a geneticist use pedigrees? 30. What is a pedigree? 31. No two people have the same DNA, except for 32. One parent of a child has type A blood and the other has type B blood. What is the child’s blood type? 33. A carrier is a person who has 34. What must occur for a girl to be colorblind? 35. Hemophilia is caused by a(n) Modified True/False Indicate whether the statement is true or false. If false, change the identified word or phrase to make the statement true. ____ 36. When Mendel crossed purebred short plants with purebred tall plants, all of the offspring were short. ____ 37. A hybrid is the offspring of parents that have different alleles for a trait. ____ 38. A pea plant that is heterozygous for tall stems has the alleles Tt. ____ 39. A Punnett square shows all the possible combinations of alleles in parents. ____ 40. An organism’s physical appearance is its phenotype. ____ 41. The sex cells produced by meiosis have twice the number of chromosomes as the parent cells. ____ 42. Chromosomes carry genes from parents to offspring. ____ 43. Even if a gene has multiple alleles, a person cannot have more than three of those alleles. ____ 44. Trait such as height and skin color that have many different phenotypes are often controlled by a single gene. ____ 45. A person’s environment can affect his or her genotype for certain traits, such as height. ____ 46. Sex-linked traits that are controlled by recessive alleles are more likely to show up in males. ____ 47. A male is represented by a square in a pedigree. Completion Complete each statement. 48. The offspring of a ____________________ plant will always have the same alleles for a trait as the parent. 49. Mendel used ____________________-pollination to produce purebred plants. 50. If a ____________________ allele is present, its trait will appear in the organism. 51. In pea plants, the tall-stem allele and the short-stem allele are different forms of the same ____________________. 52. If D represents the dominant allele of a gene, then ____________________ represents the recessive allele. 53. Mendel used the principles of ____________________ to predict what percent of offspring would show a particular trait. 54. If each of ten events is equally likely to occur, the probability of each individual event occurring is ____________________ percent. 55. A chart used to predict results of genetic crosses is known as a(n) ____________________. 56. In a cross between two hybrid Tt pea plants, ____________________ percent of the offspring will be Tt. 57. An organism that has two dominant or two recessive alleles is said to be ____________________ for that trait. 58. Alleles that are neither dominant nor recessive produce an inheritance pattern known as ____________________. 59. Genes are located on structures called ____________________. 60. The process in which a parent cell divides twice to produce sex cells is called ____________________. 61. If all of the sex cells of an organism have the T allele, the genotype of that organism must be ____________________. 62. When many genes control a trait, the trait will show a large number of ____________________. 63. Various combinations of ____________________ at each of several genes control human skin color. 64. Improvements in medical care and in ____________________ have altered the effects of genes on height. 65. A person’s surroundings, or ____________________, can change the effects of a person’s genes. 66. An egg that is fertilized by a sperm cell with a(n) ____________________ chromosome will develop into a female. 67. A recessive allele can be passed to offspring by a(n) ____________________ who does not show the trait. 68. A(n) ____________________ is a used to track the occurrence of a trait in a family. 69. A person who has the genetic disorder called ____________________ bleeds easily. 70. A gene is said to have multiple alleles if it has more than ____________________ alleles. Short Answer Use the diagram to answer each question. 71. Which trait - white flowers or purple flowers - is controlled by a dominant allele? Which is controlled by a recessive allele? How do you know? 72. In which generation are the parents purebred? In which generation are they hybrids? 73. In the F1 generation, what is the genotype of the offspring? What is their phenotype? 74. In the F2 generation, what percent of the offspring have purple flowers? What is the genotype of the purple-flowered offspring? 75. In the F2 generation, what percent of the offspring have white flowers? What are the genotypes of the white-flowered offspring? 76. Suppose one of the parents of the F2 generation had been ww instead of Ww. What percent of the offspring would have purple flowers? What percent would have white flowers? Use the diagram to answer each question. 77. What do the circles in the pedigree represent? What do the squares represent? 78. Which pairs of individuals in the pedigree have children? 79. Which individuals have the trait that is traced by the pedigree? 80. Which individuals are carriers of the trait that is traced by the pedigree? Essay 81. In pea plants, green pod color is controlled by a dominant allele. Yellow is controlled by a recessive allele. Explain why a plant with yellow pods can never be a hybrid. 82. A woman gives birth to a son. Two years later, she gives birth to another son. What is the probability that her third child will be a girl? Explain your reasoning. 83. Some clover plants have leaves with a white stripe. Other clover plants have leaves with a white spot. When these two types of plants are crossed, the leaves of the offspring have a white stripe and a white spot. Explain how this inheritance pattern occurs. 84. Explain the function of meiosis. 85. Explain why Mendel’s cross of purebred tall and short pea plants resulted in only tall plants. 86. In pea plants, the allele for smooth pods (S) is dominant over the allele for pinched pods (s). Construct a Punnett square that shows a cross between an SS plant and an Ss plant. Predict what percent of the offspring are likely to have smooth pods. 87. Human eyes come in a variety of colors ranging from light blue to very dark brown. Explain why eye color is not likely to be controlled by a single gene. 88. Is it possible for a son to inherit an allele on an X chromosome from his father? Explain why or why not. 89. A person with blood type AB has the alleles IA and IB. A person with blood type O has the alleles ii. Is it possible for a person with blood type AB to have a child with blood type O? Explain why or why not.