GENETICS PRACTICE QUESTIONS

Transcription

1 Mr. Lastowski Biology I Honors GENETICS PRACTICE QUESTIONS 1. Using the results of his experiments with pea plant crosses, what did Gregor Mendel discover? the laws of dominance, segregation, and independent assortment that pea plants develop mutations after exposure to radiation intermediate inheritance and gene linkage that DNA is involved in the inheritance of dominant traits 2. The puppies shown in the photograph below are all from the same litter. 5. A child has brown hair and brown eyes. His father has brown hair and blue eyes. His mother has red hair and brown eyes. Which statement best explains why the child has brown hair and brown eyes? a gene mutation occurred that resulted in brown hair and brown eyes gene expression must change in each generation so evolution can occur the child received genetic information from each parent cells from his mother's eyes were present in the fertilized egg 6. A cross between two mice with long tails and brown fur produced the four types of offspring listed below: long tailed with brown fur long tailed with white fur short tailed with brown fur short tailed with white fur Which genetic mechanism best explains the results of this cross? The differences seen with this group of puppies are most likely due to overproduction and selective breeding mutations and elimination of genes evolution and asexual reproduction sorting and recombination of genes 3. What most directly causes variation in the offspring of sexually reproducing organisms? sorting and recombining of genes replication and cloning the need to adapt and maintain homeostasis overproduction of offspring and competition 4. Two pea plants, hybrid for a single trait, produce 60 pea plants. Approximately how many of the pea plants are expected to exhibit the recessive trait? intermediate inheritance gene linkage independent assortment crossing-over 7. In a certain type of plant, tall is dominant over short, and green seed coat is dominant over yellow seed coat. When two plants heterozygous for both of these traits are crossed, the offspring produced are tall, with green seed coats; tall, with yellow seed coats; short, with green seed coats; and short, with yellow seed coats. What do the results of this cross illustrate? vegetative propagation mutagenic agents intermediate inheritance independent assortment 8. In humans, the gene for polydactyly (having extra fingers or toes) is dominant over the gene for the normal number of digits. If parents who are both homozygous dominant for polydactyly have four children, how many of these children would most likely have extra fingers or toes?

2 9. What term would best be used to describe an organism possessing two identical genes for a trait? heterozygous hybrid homozygous incompletely dominant 10.A boy has brown hair and blue eyes, and his brother has brown hair and brown eyes. The fact that they have different combinations of traits is best explained by the concept known as multiple alleles incomplete dominance sex linkage independent assortment 11.Which genetic concepts best explain the fact that hybrid parents can produce offspring with recessive phenotypes? codominance and polyploidy intermediate inheritance and segregation segregation and recombination polyploidy and recombination 12. When red-flowered snapdragons are crossed with white-flowered snapdragons, all the F1 plants will have pink flowers. If Mendel had used snapdragons instead of pea plants, he would have had difficulty in formulating his principle of dominance sex-linked traits multiple alleles mutation 13. The diagram below represents the inheritance of stem height in garden peas. The diagram best illustrates intermediate inheritance segregation and recombination sex linkage and codominance independent assortment 14. For a given trait, the two genes of an allelic pair are not alike. An individual possessing this gene combination is said to be homozygous for that trait heterozygous for that trait recessive for that trait pure for that trait 15. In a certain species of mouse, gray fur (G) is dominant over cream-colored fur (g). If a homozygous gray mouse is crossed with a cream-colored mouse, the genotype of the F1 generation will most likely be 100% Gg 50% GG and 50% gg 25% GG, 50% Gg, and 25% gg 75% Gg and 25% gg 16. Kernel color in corn is a trait determined by two alleles. The dominant allele (P) produces a purple color, and the recessive allele (p) produces a yellow color. The diagram below shows an ear of corn produced by crossing two corn plants. The shaded kernels are purple, and the unshaded ones are yellow. What can the yellow kernels best be described as? homozygous dominant heterozygous hybrid homozygous recessive 17. F represents the gene for brown coat color and f represents the gene for white coat color. In the cross FF x ff all the offspring have a brown coat. Which genetic principle is illustrated by this cross? crossing-over multiple alleles codominance dominance 18. Which genotype illustrates codominance of alleles that control blood type in humans? ii I A i I B I B I A I B

3 19. In canaries, the gene for singing (S) is dominant over the gene for non-singing (s). When hybrid singing canaries are mated with non-singing canaries, what percentage of the offspring is likely to possess the singing trait? 0% 25% 50% 100% 20. In squirrels, the gene for gray fur (G) is dominant over the gene for black fur (g). If 50% of a large litter of squirrels are gray, the parental cross that produced this litter was most likely GG Gg GO GO Gg gg gg gg 21. In a population of dogs, curly hair is dominant over straight hair. If two parents are heterozygous for this trait, what is the probability that any of their offspring will have straight hair? 0% 25% 75% 100% 22. In dogs, wire hair ( is dominant over smooth hair (d). If two wire-haired dogs produce a smooth-haired pup, the genotypes of the parent dogs are most likely DD anddd Dd and Dd DD and DD Dd and dd 23. In screech owls, red feathers are dominant over gray feathers. If two heterozygous red-feathered owls are mated, what percentage of their offspring would be expected to have red feathers? 25% 50% 75% 100% 24. The gene for tallness (T) is dominant over the gene for shortness (t) in pea plants. A homozygous dominant pea plant is crossed with a heterozygous pea plant, and 200 seeds are produced. Approximately how many of these seeds can be expected to produce plants that are homozygous dominant? In pea plants, the trait for tall stems is dominant over the trait for short stems. If two heterozygous tall plants are crossed, what percentage of the offspring would be expected to have the same phenotype as the parents? 25% 50% 75% 100% 26. In summer squash, white-colored fruit is dominant over yellow-colored fruit. If homozygous yellow-fruited plants are crossed with heterozygous white-fruited plants, what is the expected percentage of fruit color produced in the offspring? 100 % yellow 100% white 50% yellow, 50% white 25% yellow, 75% white 27. Only red tulips result from a cross between homozygous red and homozygous white tulips. This illustrates the principle of independent assortment dominance segregation incomplete dominance 28. In humans, the trait for polydactyly (having extra fingers and toes) is dominant over the gene for the normal number of digits. Which bar graph best represents the expected percentages of phenotypes among the offspring produced by a heterozygous polydactyl individual and a homozygous recessive individual? 29. Two mice that are heterozygous for black coat color are mated. Assuming coat color in mice is controlled by a single pair of genes, which genotypic ratio for coat color is expected in the offspring? 1:2:1 9:7 3:1 1:3:1

4 30. The chart below indicates a method of representing traits in pea plants. Some offspring of a cross in pea plants were tall and green. According to the chart, these plants could be represented by TTYY Ttyy ttyy TtYy 31. In pea plants, the long-stem trait (L) is dominant and the short-stem trait (l) is recessive. Two pea plants were crossed, producing seeds that yielded 165 long-stem plants and 54 short-stem plants. The genotypes of the parent plants were most likely Ll and LL ll and ll Ll and Ll LL and ll 32. Base your answer to the following question on the Punnett square below which shows the cross between two squash plants. Which genetic principle is best illustrated by the phenotype of the offspring? codominance intermediate inheritance independent assortment dominance 33. In minks, the gene for brown fur ( is dominant over the gene for silver fur (b). Which set of genotypes represents a cross that could produce offspring with silver fur from parents that both have brown fur? Bb Bb BB bb BB Bb Bb bb 34. In watermelon plants the allele for solid green fruit (G) is dominant over the allele for striped fruit (g). Pollen from a flower of a homozygous green watermelon plant is used to pollinate a flower from a heterozygous green watermelon plant. What percent of the offspring of this cross will bear striped watermelons? 0% 25% 50% 100% 35. In certain rats, black fur is dominant over white fur. If two rats, both heterozygous for fur color, are mated, their offspring would be expected to have four different genotypes and two different colors two different genotypes and three different colors three different genotypes and two different colors three different genotypes and three different colors 36. B represents the dominant allele for a trait and b represents the recessive allele. In which pair of crosses must all of the offspring produced have the same phenotype? Bb bb and Bb Bb Bb bb and BB Bb BB Bb and BB bb BB BB and Bb Bb 37. In humans, the ability to roll the tongue is dominant over the inability to roll the tongue. If two parents who are homozygous dominant for this trait have 8 children, how many children would be expected to be unable to roll their tongues? When a brown mink and a silver-blue mink were crossed, all of the offspring produced were brown. When these offspring were mated, they produced 60 brown minks and 20 silver-blue minks. Of the 60 brown minks, the number that are heterozygous should be closest to Changes in the genetic code of a human can be transmitted to offspring if they occur in cancer cells gametes cell membranes antibodies

5 40. Base your answer to the following question on Two generations of offspring of four o'clock plants are shown in the diagram below. The phenotypic ratio of the F2 generation is 3:1 2:1:2 2:1 1:2:1 41. In rats, black coat color is dominant over white coat color. If some of the offspring of a cross between a black rat and a white rat are white, the black rat must have been a polyploid homozygous heterozygous a mutation 42. A cross between two tall garden pea plants produced 314 tall plants and 98 short plants. The genotypes of the tall parent plants were most likely TT and tt TT and Tt Tt and Tt TT and TT 43. Which is a true statement about people with the genotype I A I B for blood type? They have two alleles that are codominant. They exhibit a type O phenotype. They are homozygous for blood type A. They can have only type O children. 44. When two four-o'clock plants are crossed, 48 pink four-o'clocks and 52 white four-o'clocks are produced. The phenotypes of the parents are pink and white pink and red pink and pink red and white 45. When roan cattle are crossed, 25% of the offspring produced will have white coats, 50% will have roan coats, and 25% will have red coats. What do these results illustrate? polyploidy crossing-over codominance sex linkage 46. Crosses between white-coated cattle (C W C W ) and red-coated cattle (C R C R ) produce roan offspring (C R C W ). This type of inheritance pattern is known as multiple allele inheritance crossing-over sex linkage codominance 47. If two roan cattle are crossed, what percent of the offspring are expected to show the parental phenotype for coat color? 25% 50% 75% 100% 48. A boy inherits genes for tallness, but his growth is limited as a result of poor nutrition. This is an example of an inherited disorder environmental influence on gene expression expression of a hidden trait a characteristic controlled by more than one pair of genes 49. Identical twins separated at birth and raised by different parents were found to have dramatically different personalities. This finding provides evidence for mutation and genetic recombination independent assortment segregation of alleles environmental influence on gene expression

6 50. Although identical twins inherit exact copies of the same genes, the twins may look and act differently from each other because a mutation took place in the gametes that produced the twins the expression of genes may be modified by environmental factors the expression of genes may be different in males and females a mutation took place in the zygote that produced the twins 51. Scientific studies show that identical twins who were separated at birth and raised in different homes may vary in height, weight, and intelligence. The most probable explanation for these differences is that original genes of each twin increased in number as they developed one twin received genes only from the mother while the other twin received genes only from the father environments in which they were raised were different enough to affect the expression of their genes environments in which they were raised were different enough to change the genetic makeup of both individuals 52. Identical twins were born with genes for a genetic disorder that can be controlled by diet. Both twins were placed on this diet, which excludes a certain amino acid. However, one twin chose not to follow the diet and developed the genetic disorder. The other twin followed the diet and did not develop the disorder. This difference between the twins illustrates that gene expression is not influenced by biochemical factors identical twins do not always have the same genotype gene expression is influenced by the environment the genetic disorder is inherited by identical twins, only 53. Which cross could produce a child with blood type A? I A i ii I A I A I B I B I A i I B I B I B I B ii 54. Base your answer to the following question on Which statement best explains the change shown in the diagram below? Gene expression in an organism can be modified by interactions with the environment. Certain rabbits produce mutations that affect genes in specific areas of the body. Sorting and recombination of genes can be influenced by very cold temperatures. Molecular arrangement in existing proteins can be altered by environmental factors. 55. The warmer areas of the body of a Siamese cat have light fur, and the cooler areas, such as the ears and feet, are covered with dark fur. A specific enzyme controls the production of the pigment that causes the fur to become dark. One inference that could be drawn about the enzyme that controls dark pigment formation is that it is more active at cooler temperatures more active at warmer temperatures denatured at cooler body temperatures affected by an acidic ph 56. According to the gene-chromosome theory, which statement is true? Genes are present only on human chromosomes. Genes are arranged in a linear sequence on a chromosome. Alleles are located on nonhomologous chromosomes. Mutations occur mainly in sex cells 57. The genes for red hair and freckles are usually inherited together because these genes are homologous sorted independently linked hybrid traits

7 58. A certain species of moth may have antennae that are feathery or non-feathery. Those with feathery antennae usually have red eyes, and those with non-feathery antennae usually have white eyes. If antenna type and eye color are each controlled by a single pair of genes, a valid conclusion that can be drawn regarding the genes for antenna type and eye color is that these genes are on separate chromosomes linked polyploid found at the same locus 59. When a person's teeth are being x rayed, other body parts of this person are covered with a protective lead blanket to prevent loss of hair increase in cell size changes in DNA molecules changes in glucose structure 60. Which situation would most directly affect future generations naturally produced by a maple tree? Ultraviolet radiation changes the DNA sequence within some leaves of the tree. Ultraviolet radiation changes the DNA sequence within the gametes of some flowers of the tree. An increase in temperature reduces the number of cell divisions in the roots. Rapidly growing cells just under the bark are exposed to radiation, causing changes in genetic material. 61. In some individuals, G A G, the codon for glutamic acid, is changed to G U G, the codon for valine. This error causes red blood cells to have a significant change in shape. This genetic disorder is known as albinism hemophilia Tay-Sachs sickle-cell anemia 62. Which cross could produce a child with type O blood? I A i I B I B I A I A I B i I A I B ii I A i I B i 63. Base your answer to the following question on the pedigree chart below and on your knowledge of biology. The chart shows the inheritance of Tay-Sachs in a family. What can be determined about Blanche's parents? Neither parent has the allele for Tay-Sachs. One parent has Tay-Sachs and the other is normal. One parent has the allele for Tay-Sachs and the other does not. Both parents have the allele for Tay-Sachs. 64. Which human genetic disorder results in the condition illustrated by the drawing below of a blood sample? Down's syndrome Tay-Sachs disease sickle-cell anemia hemophilia 65. A man with normal color vision married a woman with normal color vision. The father of the woman was colorblind. If this couple had a daughter, what is the chance this child would be colorblind? 0% 25% 50% 100%

8 66. The pedigree chart below represents the inheritance of sickle-cell anemia through three generations. 70. Base your answer to the following question on the information and diagram below and on your knowledge of biology. In cats, gene E produces yellow fur and gene B produces black fur. A cat that inherits both of these genes has patches of yellow and black fur and is known as a calico. The alleles for black or yellow are located on the X -chromosome. The cross X B Y X B X E is illustrated in the square below. Which symbols could be used to represent individual 9 in generation III? Base your answers to questions 67 through 69 on the pedigree chart below which shows a history of blood types. 67. The blood types of the individuals represented in the chart by 7 and 8 could be A or B, only AB, only A, B, or AB, only A, B, AB, or O 68. Which individuals represented by the chart must be homozygous for blood type? 1 and 2 2 and 3 3 and 4 1 and The genotype of the individual represented in the chart by 5 is I a I a I a i ii I a I b Yellow male offspring are represented by A mother pregnant with her fourth child remarked, "This one just has to be a boy. It is almost certain, since my other three children are girls." Which statement best indicates the accuracy of the mother's comment? The mother is wrong because the chance of having a boy is always 50%. The mother is wrong because there is only a 25% chance that the child will be a boy. The mother is right because the genes of the father are dominant over those of the mother. The mother is right because a child usually inherits both sex chromosomes from the mother. 72. Which diagram illustrates fertilization that would most likely lead to the development of a normal human female?

9 Base your answers to questions 73 through 75 on the pedigree chart below. The pedigree chart represents the inheritance of color blindness through three generations. 73. Which statement about the genotype of Linda and Donna regarding color blindness is correct? Both carry one recessive allele. Linda is a carrier, and Donna is homozygous dominant. Both are homozygous recessive. Linda is homozygous dominant, and Donna is a carrier. 74. Where is the allele for color blindness carried? on the Y-chromosome, only on the X-chromosome, only on both the X- and Y-chromosomes on neither the X- nor the Y-chromosome 75. Barbara is expecting another child. What is the probability that the new baby will be colorblind? 0% 25% 50% 100%

10 76. Base your answer to the following question on The pedigree chart below shows the pattern of inheritance for a sex-linked trait. 77. If a woman who is heterozygous for hemophilia marries a normal man, which will be true of their offspring? All of their sons will be hemophiliac. All of their daughters will be carriers of hemophilia. One-half of their daughters may be hemophiliac. One-half of their children of either sex may receive the abnormal allele. If this couple has another son, what is the probability that he will exhibit this sex-linked trait? 0% 25% 50% 100%

11 Answer Key ClassicalGenetics 1. A 2. D 3. A 4. A 5. C 6. C 7. D 8. D 9. C 10. D 11. C 12. A 13. B 14. B 15. A 16. D 17. D 18. D 19. C 20. C 21. B 22. B 23. C 24. C 25. B 26. C 27. B 28. B 29. A 30. B 31. C 32. D 33. A 34. A 35. C 36. C 37. A 38. C 39. B 40. D 41. C 42. C 43. A 44. A 45. C 46. D 47. B 48. B 49. D 50. B 51. C 52. C 53. A 54. A 55. A 56. B 57. C 58. B 59. C 60. B 61. D 62. D 63. D 64. C 65. A 66. B 67. D 68. D 69. B 70. D 71. A 72. A 73. A 74. B 75. C 76. C 77. D