Full file at CHAPTER 2 Genetics

Transcription

1 CHAPTER 2 Genetics MULTIPLE CHOICE 1. Chromosomes are a. small linear bodies. b. contained in cells. c. replicated during cell division. 2. A cross between true-breeding plants bearing yellow seeds produces offspring bearing a. yellow seeds. b. 1/2 yellow and 1/2 green seeds. c. untrue-breeding seeds. d. none of the above ANS: A DIF: 1 3. Cross-breeding the offspring of green and yellow peas led to in the second generation. a. only green individuals surviving the first days of life b. a 3:1 ratio of yellow to green offspring c. yellowish-green individuals d. half the offspring being green and the other half yellow ANS: B DIF: 2 4. Gametes a. are not involved in the transmission of genes. b. are the sex cells, or eggs and sperm. c. do not differ between male and female animals. d. were discovered by Darwin. ANS: B DIF: 1 5. Mendel s first law (of segregation) states that a. characteristics from the parents blend together to produce intermediate offspring. b. characteristics from the parents do not blend together in offspring. c. paternally and maternally derived characteristics segregate into gametes during meiosis. d. b and c only 6. Mendel s second law (of independent assortment) states that a. the probability of inheriting one trait does not affect the probability of inheriting another trait. b. the probability of inheriting one trait does affect the probability of inheriting another trait. c. the probability of inheriting one trait is never equal to the probability of inheriting another

2 trait. d. traits on the same chromosome cannot assort into gametes. ANS: A DIF: 2 7. Mendel s second law (of independent assortment) states that a. eggs and sperm are formed independently of one another. b. transmission includes both blending and particulate inheritance. c. particles inherited from the mother and the father are equally likely to be transmitted to offspring. d. b and c only ANS: C DIF: 3 8. Chromosomes are contained in a. the gametes. b. the nucleus of the cell. c. every cell of the body. 9. Homologous chromosomes a. come in pairs. b. are similar in size and staining pattern. c. are found in primates. 10. Mitosis a. involves duplication of a set of chromosomes. b. results in a daughter cell that has an exact copy of the chromosomes of its parent. c. results in cells that contain the same chromosomes that were present when the egg and sperm united. 11. Reduction of chromosome number occurs during a. recombination. b. meiosis. c. somatic cell formation. d. linked genes. ANS: B DIF: A pea plant with only green seeds is a. homozygous recessive. b. always tall.

3 c. an example of blending inheritance. d. b and c only ANS: A DIF: If you have two parents with the genotype Aa, what is the chance that they will have an offspring with the genotype AA? a. 1/8 b. 1/2 c. 1/4 d. 1/16 ANS: C DIF: The possible genotype of a pea plant with yellow seeds is a. AA. b. aa. c. Aa. d. a and c only 15. In diploid organisms a. chromosomes occur in homologous pairs. b. chromosomes occur in homologous triplets. c. meiosis produces haploid gametes. d. a and c only 16. In mitosis a. a haploid cell divides into two diploid cells. b. a diploid cell divides into two haploid cells. c. a haploid cell divides into two diploid cells. d. a diploid cell divides into two diploid cells. 17. Which of the following is (are) true of mitosis? a. Mitosis produces identical daughter cells. b. Mitosis produces nonidentical daughter cells. c. Mitosis produces cells with different chromosomes. d. b and c only ANS: A DIF: In meiosis a. haploid cells are produced from a single diploid cell. b. haploid cells are produced from two diploid cells. c. diploid cells are produced from a single diploid cell.

4 d. diploid cells are produced from two haploid cells. ANS: A DIF: Which of the following is (are) true of meiosis? a. Daughter cells contain one chromosome from each homologous pair. b. Daughter cells contain both chromosomes from each homologous pair. c. Meiosis produces sex cells. d. a and c only 20. Gametes a. contain one of each pair of homologous chromosomes. b. are responsible for normal body growth of organisms. c. can be eggs or sperm. d. a and c only 21. Which sequence is correct? a. diploid individual haploid gamete diploid zygote body growth b. diploid individual meiosis fertilization mitosis c. diploid individual mitosis zygote formation diploid individual ANS: D DIF: A zygote is a. a single cell. b. a union of two gametes. c. a cell that may undergo mitosis. 23. An allele a. is a form of a gene. b. contributes to an individual phenotype. c. contributes to an individual genotype. 24. The genotype of an individual refers to a. its visible characteristics. b. the number of chromosomes in its sex cells. c. the number of chromosomes in its body cells. d. none of the above

5 25. The phenotype of an individual refers to a. its visible characteristics. b. the number of homologous pairs of chromosomes. c. the number of chromosomes in its body cells. d. the number of chromosomes in its sex cells. ANS: A DIF: An individual with two identical alleles at a locus is a. an independent phenotype. b. a homozygote. c. a heterozygote. d. dominant. ANS: B DIF: A heterozygote is an individual with a. the same paternal and maternal allele at a particular locus. b. a different paternal and maternal allele at a particular locus. c. a recessive allele. d. a and c only ANS: B DIF: True-breeding plants bearing yellow seeds have what genotype? a. aa b. aa c. Aa d. AA 29. When Mendel crossed true-breeding plants bearing yellow seeds with true-breeding plants bearing green seeds, what was the phenotypic ratio among the F 1 offspring? a. all aa individuals b. all AA individuals c. 1/2 yellow and 1/2 green individuals d. all yellow individuals 30. True-breeding plants bearing green seeds have what genotype? a. aa b. aa c. Aa d. AA ANS: A DIF: 1

6 31. When a true-breeding plant bearing yellow seeds produces gametes, what alleles are represented among those gametes? a. only A alleles b. only a alleles c. both a and A alleles, in equal frequencies d. both a and A alleles, but mostly A alleles ANS: A DIF: When Mendel crossed true-breeding plants bearing yellow seeds with true-breeding plants bearing green seeds, what was the genotypic ratio among the F 1 offspring? a. all aa individuals b. all AA individuals c. all Aa individuals d. all green individuals ANS: C DIF: When Mendel crossed individuals from the F 1 generation with each other, what was the genotypic ratio among the offspring? a. all Aa or aa b. 25% aa, 50% Aa/aA, and 25% AA c. all AA or aa d. 33.3% aa, 33.3% Aa/aA, and 33.3% AA ANS: B DIF: When Mendel crossed individuals from the F 1 generation with each other, what was the phenotypic ratio among the offspring? a. all yellow b. 1/2 green and 1/2 yellow c. 3/4 yellow and 1/4 green d. 3/4 green and 1/4 yellow ANS: C DIF: The probability of an offspring getting two A alleles, one from the father and one from the mother, is a. 50%. b. 25%. c. 12.5%. d. 12.5%. ANS: B DIF: When Mendel crossed heterozygote pea plants for two different traits, he recorded a phenotypic ratio of a. 1:2:1. b. 4:8:4.

7 c. 9:3:3:1. d. 12:4. ANS: C DIF: Recombination and crossing-over are very important in the genetic process because they produce a. variation. b. a new somatic cell. c. DNA. d. linked chromosomes. ANS: A DIF: What is the probability that an Aa individual will produce a gamete with an A allele? a. 100% b. 75% c. 50% d. 25% ANS: C DIF: Consider a cross between tall and short plants in which all of the offspring are tall. This suggests that a. the allele for tall is recessive. b. the allele for tall is dominant. c. the alleles for tall and short are codominant. d. none of the above ANS: B DIF: What is the probability of a heterozygote for seed coat and color having an ab gamete? a. 100% b. 50% c. 25% d. 0% ANS: C DIF: Mendel crossed AABB with aabb individuals, where B = smooth, b = wrinkled, A = yellow, and a = green. What was the genotypic ratio of the F 1 generation? a. all AAbb b. 1/2 AAbb and 1/2 aabb c. all AaBb d. all AABB ANS: C DIF: Imagine a cross between AA and Aa individuals. What is the genotypic ratio among the offspring? a. 1/2 AA and 1/2 aa b. 1/2 Aa and 1/2 aa c. 1/2 AA and 1/2 Aa

8 d. all AA ANS: C DIF: Under which circumstance does Mendel s law of independent assortment hold? a. only when traits are tightly linked (close together) on the same chromosome b. only when traits are on different chromosomes c. only when there is crossing over d. a and c only ANS: B DIF: Independent assortment states that a. the fact that a gamete has an A rather than an a allele does not influence the probability that it will have a B rather than a b allele. b. alleles at different loci do not influence each other as they assort into gametes. c. dominant alleles act independently of recessive alleles. d. a and b only 45. Which of the following is (are) true of chromosomes? a. Hereditary material is contained in the chromosomes. b. Chromosomes come in pairs. c. One chromosome from each homologous pair is passed on to daughter cells during meiosis. 46. Imagine two loci on one chromosome. At one locus, the genotype is Aa and at the other locus, the genotype is Bb. After meiosis, what are all of the possible genotypes of the gametes? a. AB and ab gametes b. all AB gametes c. AB, ab, Ab, and ab gametes d. Ab and ab gametes ANS: C DIF: Crossing over a. occurs when homologous pairs of chromosomes exchange material. b. increases genetic combinations. c. can occur between loci on the same chromosome. ANS: D DIF: When two loci are very close together on a chromosome a. they are linked. b. a crossing-over event between them is less likely than when two loci are far apart.

9 c. they can blend into a single gene. d. a and b only 49. Molecular genetics a. produces new discoveries in medicine and agriculture. b. links biology to chemistry and physics. c. provides data for reconstructing the evolutionary history of species. TOP: Molecular Genetics 50. Two traits are less likely to assort independently if a. the loci are on the same as opposed to different chromosomes. b. the loci are far apart as opposed to close together on the same chromosome. c. they are heterozygous. d. a and b only ANS: A DIF: Modern molecular genetics a. resulted from the discovery of the structure of DNA. b. links biology to chemistry and physics. c. provides important data for reconstructing evolutionary history. TOP: Molecular Genetics 52. Analysis of DNA sequences tells us a. that humans and chimpanzees share a more recent common ancestor than either shares with gorillas. b. that the last common ancestor of chimpanzees and human lived between 5 and 7 mya. c. when the first modern humans left Africa and where they went. TOP: Molecular Genetics 53. DNA is a complex molecule with many alternative forms that are equally stable chemically, which allows a. the double helix to form. b. independent evolution. c. the message that DNA carries to be transmitted faithfully. d. continuous variation. ANS: C DIF: 2 TOP: Molecular Genetics 54. The structure of DNA is that of a. a series of intertwining chromosomes. b. a double-stranded molecule, consisting of four bases. c. a series of nucleotides: adenine, guanine, thymine, and cytosine. d. b and c only TOP: Molecular Genetics

10 55. Are any of the following statements true? a. DNA has a nonrepeating four-base structure. b. DNA is contained in chromosomes. c. DNA stands for determining nuclear acid. d. DNA does not tell us why heredity leads to the patterns Mendel described in pea plants. ANS: B DIF: 1 TOP: Molecular Genetics 56. Exact replication of DNA is possible due to a. the low number of possible nucleotides. b. base-pair complementarity. c. the sequence of nucleotides along the DNA, which is always the same. d. a and c only ANS: B DIF: 1 TOP: Molecular Genetics 57. Sickle-cell anemia a. is common among people of West Africa. b. is caused by a single amino acid change in the hemoglobin molecule. c. results when hemoglobin molecules do not fold correctly, reducing their ability to bind to oxygen. TOP: Molecular Genetics 58. Unlike a eukaryote, a prokaryote a. does not have a cell nucleus. b. has uninterrupted DNA sequences that code for proteins. c. lacks chromosomes. ANS: D DIF: 3 TOP: Molecular Genetics 59. Alternative splicing a. involves the snipping out of intron-based parts of mrna. b. means that some entrons are not included when the mrna is spliced back together. c. allows the same DNA sequence to code for more than one protein. ANS: D DIF: 3 TOP: Molecular Genetics 60. Some biologists hypothesize that introns are maintained in eukaryotes because their population sizes are much smaller than in prokaryotes. is the random, nonadaptive evolutionary process that explains this phenomenon. a. Genetic drift b. Natural selection c. Protein synthesis d. Transcription ANS: A DIF: 3 TOP: Molecular Genetics 61. The mrna codon for the amino acid TGG is, and its trna anticodon is. a. AGG; UCC b. GGT; CCA c. GTG; CAC

11 d. UGG; ACC TOP: Molecular Genetics 62. Within DNA are properties that specify a. the linear sequence of amino acids in a protein (primary structure). b. the way in which the protein folds up (tertiary structure). c. the function of the protein. TOP: Molecular Genetics 63. Which of the following is (are) true of DNA transcription/translation? a. A codon corresponds to an amino acid. b. A DNA sequence codes for a protein. c. A protein consists of a series of codons. d. a and b only TOP: Molecular Genetics 64. Because there are 64 possible codons and only 20 amino acids a. many mutations have no effect on phenotype. a. every mutation has some effect on phenotype. Genetics / 155 b. each trna molecule contains two extra amino acids. c. each trna molecule contains two extra codons. ANS: A DIF: 2 TOP: Molecular Genetics 65. Which of the following sequences is accurate for transcription and translation? a. DNA trna mrna protein b. DNA mrna protein c. Protein trna DNA d. Protein trna DNA ANS: B DIF: 2 TOP: Molecular Genetics 66. As DNA codes for proteins it can be interrupted by noncoding sequences called a. organelles. b. proteins. c. introns. d. synthetases. ANS: C DIF: 1 TOP: Molecular Genetics 67. The presence of repressors and activators in regulatory genes means that there is of gene expression. a. translation b. combinational control c. a biochemical pathway d. primary structure ANS: B DIF: 2 TOP: Molecular Genetics 68. The organelles that splice the mrna in eukaryotes after the introns have been snipped out are called a. splitsomes. b. mergesomes.

12 c. splicesomes. d. unitesomes. ANS: C DIF: 1 TOP: Molecular Genetics 69. binds to complementary mrna molecules and prevents them from being translated into a protein. a. Transfer RNA b. MicroRNA c. Junk DNA d. Intron RNA ANS: B DIF: 2 TOP: Molecular Genetics 70. At least of the genome is expressed as noncoding DNA. a. 50% b. 25% c. 75% d. 5% ANS: A DIF: 1 TOP: Molecular Genetics TRUE/FALSE 1. When Mendel s work was rediscovered in 1900, it still was not widely accepted because scientists still did not know anything about chromosomes. ANS: F DIF: 1 2. Mendel s law of segregation states that inherited material comes in pairs, and particles from each pair separate into gametes. 3. Darwin understood how genetic inheritance works. ANS: F DIF: 1 4. Mendel found that crosses between plants that produce green peas always produce offspring with green peas. 5. When a human cell divides, 23 pairs of chromosomes appear in its nucleus, including a pair of sex chromosomes. 6. Zygotes divide mitotically and gametes are produced through meiosis.

13 7. Cells spend most of their time in a resting period, doing what they are supposed to do as bone cells, organ cells, muscle cells, and so on. 8. Haploid sperm meet diploid ova to produce a new individual. ANS: F DIF: 2 9. An example of Mendel s law of independent assortment is when the color of a plant does not affect its height. ANS: T DIF: Mendel s law of independent assortment is true only if the traits under consideration are on different chromosomes. 11. As Darwin and others debated how evolution works, Mendel was working out the rules of genetic inheritance. 12. Traits that breed true change from one generation to the next. ANS: F DIF: In haploid organisms, chromosomes come in homologous pairs. ANS: F DIF: In meiosis, only half of the chromosomes are transmitted from the parent cell to the gamete. 15. A pea plant is homozygous for seed color when it has two copies of the same allele. 16. Cells spend little of their time dividing; instead, they are most often resting.

14 17. All parts of the DNA code for proteins. ANS: F DIF: 1 TOP: Molecular Genetics 18. A sequence of codons corresponds to a sequence of amino acids. TOP: Molecular Genetics 19. A codon is made up of a series of three nucleotides. TOP: Molecular Genetics 20. Because DNA consists of only a few nucleotide bases, there is a limited number of proteins it can produce. ANS: F DIF: 3 TOP: Molecular Genetics 21. Introns may serve to divide a gene into separate, functional parts. ANS: T DIF: 2 TOP: Molecular Genetics 22. Because proteins represent complex adaptations, most base changes are deleterious or harmful. ANS: F DIF: 2 TOP: Molecular Genetics 23. The real work of synthesizing proteins is performed by molecules other than DNA. ANS: T DIF: 2 TOP: Molecular Genetics 24. RNA is a facsimile of DNA, but unlike DNA it can leave the nucleus and travel into the cytoplasm. TOP: Molecular Genetics 25. Some RNA molecules are important in protein synthesis while others help to regulate the expression of other genes. TOP: Molecular Genetics 26. In eukaryotes the segment of DNA that codes for a protein is almost always interrupted by a noncoding sequence called an exon. ANS: F DIF: 1 TOP: Molecular Genetics 27. Biochemical pathways are quite simple, such as the pathway for the conversion of glucose to energy in animal cells. ANS: F DIF: 2 TOP: Molecular Genetics 28. Proteins called enzymes have only one function regulating an organism s biochemistry.

15 ANS: F DIF: 2 TOP: Molecular Genetics ESSAY 1. How do the results of Mendel s experiments affect our understanding of how variation is preserved? ANS: 2. Imagine a cross between two AaBb individuals, where A = yellow, a = green, B = smooth, and b = wrinkled. What is the genotypic and phenotypic ratio among the offspring? ANS: 3. Compare and contrast mitosis and meiosis. Include in your discussion for each process (a) the number of daughter cells produced and (b) the number of chromosomes each new cell contains. What are recombination and crossing over, and why are they important in the study of evolution? ANS: 4. Consider a homologous pair of chromosomes with the genotype Aa at one locus and the genotype Bb at another locus. After undergoing meiosis, what are all of the possible genotypes of the gametes produced? ANS: 5. Explain the life cycle of diploid organisms in terms of meiosis and mitosis. ANS: 6. Describe the structure of DNA. ANS: TOP: Molecular Genetics 7. How does a sequence of DNA produce a protein through transcription and translation?

16 ANS: Full file at TOP: Molecular Genetics 8. What is the role of regulatory genes? What is meant by the combinational control of gene expression? Illustrate your answer with an example. ANS: TOP: Molecular Genetics 9. How does alternative splicing allow the same DNA sequence to code for more than one protein? Why is alternative splicing important in eukaryotes? ANS: TOP: Molecular Genetics