Multiple Choice Identify the letter of the choice that best completes the statement or answers the question.

Transcription

1 Cell Division True/False Indicate whether the sentence or statement is true or false. 1. Tissue growth requires cell growth. 2. Cells divide rather than continue to increase in size to facilitate the exchange of materials through the cell membrane. 3. The stage between nuclear divisions in mitosis is called cytokinesis. 4. In animal cells, the separation of new cells produced by mitosis is accomplished by a cell plate that forms between the two chromatin masses. 5. A clone is a combination of the genetic material of two parent cells. 6. A cell without a nucleus is referred to as totipotent. 7. In general, cancer cells divide at slower rates than normal cells. 8. Cancer cells lack the ability to differentiate. 9. Meiosis is a process by which gametes are formed. 10. In humans, the haploid number of chromosomes is 46 and the diploid chromosome number is All daughter cells produced by meiosis are genetically identical to each other and to the parent. 12. Mitosis, combined with fertilization, explains the variation in traits that is observed in species that reproduce sexually. 13. The formation of sex cells during meiosis is referred to as gametogenesis. 14. Chromosomes that are not sex chromosomes are referred to as autosomes. 15. Down syndrome is an example of a nondisjunction disorder. Multiple Choice Identify the letter of the choice that best completes the statement or answers the question. 16. Which of the following events is not characteristic of interphase? a. The cell is inactive. b. Proteins are synthesized for the next mitotic division. c. Proteins are synthesized for cell growth and metabolism d. The genetic material duplicates in preparation for mitosis. e. The genetic material is referred to as chromatin. 17. The series of events that takes place from the formation of a cell until it divides again is called a. mitosis. d. the cell cycle. b. meiosis. e. fertilization. c. cell growth. 18. If one of two newly formed daughter cells has one extra chromosome, and the other daughter cell has one less, the problem in the preceding mitotic division probably occurred in a. prophase. d. telophase. b. metaphase. e. cytokinesis.

2 c. anaphase. 19. The proper sequence of mitosis is a. prophase, anaphase, metaphase, telophase b. prophase, telophase, anaphase, metaphase. c. metaphase, prophase, anaphase, telophase d. telophase, prophase, metaphase, anaphase e. prophase, metaphase, anaphase, telophase. 20. What is the correct sequence of the following events that occur in mitosis? 1. The cytoplasm and organelles are divided between the daughter cells. 2. The nucleolus and nuclear envelope reappear. 3. The centromere splits. 4. The chromosomes condense and the nucleolus disappears. 5. The chromosomes are pulled to the poles of the cell. 6. The chromosomes line up on the equatorial plane. a. 2, 1, 3, 6, 5, 4 d. 4, 6, 3, 5, 2, 1 b. 1, 4, 3, 5, 6, 2 e. 4, 6, 3, 2, 5, 1 c. 4, 3, 6, 5, 1, Which of the following structures disappears in prophase and reappears in telophase? a. centromeres d. spindle fibres b. cell membrane e. nuclear membrane c. chromosomes 22. During anaphase of mitosis a. centrioles divide. b. chromosomes migrate toward poles. c. asters and spindle form. d. nuclear membranes reform. e. chromosomes attach to spindle fibres 23. Select the answer which gives the correct sequence of events in the mitosis of onion root tip cells. 1. cell plate formation 2. appearance of spindle fibers 3. movement to centre of the cell 4. separation of chromatids 5. chromatin condenses a. 5, 2, 3, 4, 1 d. 5, 3, 2, 4, 1 b. 1, 4, 2, 5, 3 e. 5, 3, 4, 2, 1 c. 3, 2, 5, 4, If a cell with 36 chromosomes undergoes mitosis, each daughter cell will have a. 36 chromosomes. d. 9 chromosomes. b. 72 chromosomes. e. 6 chromosomes. c. 18 chromosomes. 25. If the centromere in one of your 46 chromosomes does not split until telophase, it would result in a. two cells, each with 46 chromosomes. b. two cells, each with 23 chromosomes. c. two cells, one with 45 chromosomes and one with 47 chromosomes. d. two cells, one with 23 chromosomes and one with 46 chromosomes. e. two cells, one with 40 and chromosomes and one with 52 chromosomes. 26. A certain cell undergoes mitosis every 20 min. The number of cells produced from one original cell after 1 h 20 min. would be a. 2. d. 80.

3 b. 16. e. 8. c Which cells in the human body have a diploid number of 46 chromosomes in their nuclei? a. all cells b. only the reproductive cells c. only cells that are produced by meiosis d. only zygotes e. only cells that are produced by mitosis 28. An important feature of meiosis is that it a. results in the production of a fertilized egg cell. b. minimizes the number of genetically different gametes. c. doubles the chromosome number between successive generations. d. maintains the same number of chromosomes in the organism between generations. e. reduces the number of chromosomes in the organism between generations. 29. A cell in a human testis is undergoing meiosis. What is the sequence of the following events? 1. A cell division occurs without the duplication of chromosomes. 2. The chromosomes replicate in interphase. 3. Haploid cells are formed. 4. Without separation of the centromere, the chromosomes move to the poles of the cell. 5. The centromere splits and the chromosomes move to the poles of the cell. a. 2, 4, 5, 1, 3 d. 2, 5, 1, 4, 3 b. 1, 5, 4, 3, 2 e. 2, 1, 5, 4, 3 c. 4, 1, 5, 2, Which statement does not describe the interphase between telophase I and prophase II of meiosis? a. Replication of DNA occurs. b. In most cells, the chromosomes have uncoiled. c. If present, centrioles migrate to opposite poles. d. In most cells, a nuclear membrane surrounds the chromosomes. e. The cells contain chromosomes with a mixture of paternal and maternal genes. 31. During meiosis, genetic variation in the gametes is achieved by a. replication and fertilization. d. crossing over and random assortment. b. crossing over and replication. e. replication and random assortment. c. crossing over and fertilization. 32. Each human cell may contain as many as genes. Most of these are represented by two copies in each of your body cells. How many copies of each gene would be in a single cell in telophase I of meiosis? a. 1 d. 4 b. 2 e. 8 c Which is a result of meiosis? a. Chromosome number is reduced to one-half the original number. b. New combinations of genes are produced when crossing over occurs. c. Maternal and paternal chromosomes are mixed when homologous chromosomes separate independently. d. Genetic variation is maintained within species. e. All of these choices are results of meiosis. 34. Classify the following statement: The resulting cells contain one chromosome from each homologous pair. a. mitosis d. neither mitosis nor meiosis b. meiosis e. both mitosis and meiosis c. fertilization

4 35. Classify the following statement: The centromere splits prior to the separation of the chromosomes. a. mitosis d. neither mitosis nor meiosis b. meiosis e. both mitosis and meiosis c. fertilization 36. Classify the following statement: The chromosomes are replicated in interphase. a. mitosis d. neither mitosis nor meiosis b. meiosis e. both mitosis and meiosis c. fertilization 37. Classify the following statement: The daughter cells have the same number of chromosomes as the parent cell. a. mitosis d. neither mitosis nor meiosis b. meiosis e. both mitosis and meiosis c. fertilization 38. Classify the following statement: This type of nuclear division helps maintain the number of chromosomes from generation to generation. a. mitosis d. neither mitosis nor meiosis b. meiosis e. both mitosis and meiosis c. fertilization 39. If one pair of your 23 pairs of chromosomes does not separate during anaphase I of meiosis, the consequence would be the production of a. four cells, each with 23 chromosomes. b. four cells, two with 23 chromosomes and two with 46 chromosomes. c. four cells, two with 45 chromosomes and two with 47 chromosomes. d. four cells, two with 22 chromosomes and two with 24 chromosomes. e. four cells, two with 23 chromosomes and two with 47 chromosomes. 40. The haploid chromosome number in humans is a. 23. d. 92. b. 46. e. 69. c If a sperm cell contains 18 chromosomes, a muscle cell from the same organism will contain a. 9 chromosomes. d. 18 pairs of chromosomes. b. 9 pairs of chromosomes. e. 27 chromosomes. c. 18 chromosomes. 42. The genetic defect known as Down Syndrome is due to a. an extra chromosome. d. a missing sex chromosome. b. a nonfunctional enzyme. e. two female sex chromosome c. linkage and crossing over. 43. How many chromosomes would occur in each body cell of a person who has combined Down/Klinefelter syndrome? a. 23 d. 47 b. 45 e. 48 c Down Syndrome a. occurs only in females. d. is caused by a missing chromosome. b. occurs in males and females equally. e. occurs only in males. c. is a result of an extra chromosome. 45. Which of the following is characteristic of meiosis but not of mitosis? a. involves cell division b. occurs in both plants and animals

5 c. results in chromosome reduction to a single set d. involves a distribution of chromosomes to daughter nuclei e. involves the movement of chromosomes 46. The events which occur in both mitosis and meiosis are similar except during a. anaphase. b. chromosomal duplications. c. mitotic metaphase and first meiotic metaphase. d. mitotic metaphase and second meiotic metaphase. e. the first interphase. 47. During which stage would it be most easy to distinguish a cell undergoing mitosis from a similar cell undergoing the first meiotic division? a. telophase d. metaphase b. prophase e. interphase c. anaphase 48. Which of the following would you find at the end of the telophase I stage of meiosis? a. one haploid cell d. one diploid cell b. two haploid cells e. two diploid cells c. four haploid cells Completion Complete each sentence or statement. 49. Cell division allows cells to, to reproduce, and to, damaged and worn tissues. 50. Early researchers divided the cell cycle into two distinct phases: i) _, ii) _. 51. During _, the cell's cytoplasm is divided into two daughter cells. 52. At the beginning of mitosis, sister chromatids are attached at a point called the _. 53. If the nucleus is removed from one egg cell and replaced with the nucleus from an embryo, the offspring is a(n) _ of the cell that donates the nucleus. 54. When cancer cells can dislodge from a tumour and move to another area, _ is occurring. 55. Meiosis produces _ cells, while fertilization produces a _ cell. 56. In the life cycle of an animal, meiosis produces _. 57. is the pairing of homologous chromosomes during meiosis. 58. The failure of chromosomes to separate during anaphase of meiosis is known as _. Matching Match each item with the correct statement below. a. cytokinesis f. haploid b. chromatid g. diploid c. centromere h. synapsis

6 d. spindle fibres i. crossing over e. metastasis j. tetrad 59. the event where a cancer cell breaks free from a tumor and moves into another tissue 60. one strand of a double-stranded chromosome 61. serve as guide wires for the movement of chromosomes 62. twice the number of chromosomes in a gamete 63. the pairing of homologous chromosomes 64. the equal division of the cytoplasm and constituent organelles 65. the number of chromosomes in a gamete 66. the exchange of material between two homologous chromosomes 67. the point of attachment for chromatids 68. a pair of homologous chromosomes, each with two chromatids Match the following stages of mitosis to the events listed below. a. interphase d. anaphase b. prophase e. telophase c. metaphase f. cytokinesis 69. cytoplasm divides 70. the chromosomes in the nucleus become visible 71. chromosomes replicate 72. spindle fibres dissolve 73. chromosomes line up at the equator 74. centromeres divide, and chromatids move to opposite poles 75. nuclear membrane forms around chromosomes 76. nuclear membrane completely dissolves 77. chromosomes condense becoming shorter and thicker 78. spindle fibres appear Match the following stages of meiosis the events listed below. a. prophase I e. prophase II b. metaphase I f. metaphase II c. anaphase I g. anaphase II d. telophase I h. telophase II 79. breaking of the attachment between the two chromatids 80. homologous chromosomes attach themselves to the spindle fibres 81. chromosomes, each with two chromatids, line up along the equatorial plate 82. four haploid cells are produced 83. homologous chromosomes move to opposite poles 84. nuclear membrane dissolves, and chromosomes come together in homologous pairs 85. nuclear membrane dissolves and the spindles begin to form, with no replication of chromosomes 86. cells are ready to enter the second stage of meiosis 87. homologous chromosomes line up along the equatorial plate 88. chromosomes under go synapsis Match the process of cell division to the following events. a. mitosis b. meiosis

7 89. daughter cells are genetically identical to each other and parent cell 90. results in two daughter cells 91. cells are haploid 92. introduces genetic variation into a species 93. daughter cells are different from each other and parent cell 94. cells are diploid 95. results in four cells 96. involves two divisions 97. involved in the production of sex cells 98. involves one division Match the chromosome number contained within each of the following cell types. a. diploid b. haploid 99. spores 100. zygote 101. sporophyte 102. gametes 103. body cells 104. gamete-producing cells in humans 105. gametophytes 106. multicellular body Match each item with the correct statement below. a. trisomy e. Turner syndrome b. monosomy f. Klinefelter syndrome c. Downs syndrome g. amniocentesis d. karyotype chart h. chorionic villus sampling 107. a procedure that involves drawing fluid from the sac surrounding the developing fetus 108. a trisomic disorder in which a male carries an XXY condition 109. the condition where there are three homologous chromosomes in place of a homologous pair 110. a picture of chromosomes arranged in homologous pairs 111. a procedure that draws cells from the outer membrane surrounding the embryo 112. a monosomic disorder in which a female has a single X chromosome 113. the condition where there is a single chromosome in place of a homologous pair in every cell of an organism 114. a trisomic disorder in which a zygote receives three homologous chromosomes for chromosome pair number 21 Short Answer 115. What is the basic function of meiosis, and why is it necessary? 116. List five differences between mitosis and meiosis Explain why two nuclear divisions are necessary to produce four haploid nuclei from a single diploid nucleus Distinguish between mitosis and cytokinesis Why is it that cells divide rather than increase in size?

8 120. Identify the events that occur during the two phases of the cell cycle Explain the differences that occur during cytokinesis in a plant and an animal cell Explain the process of cloning in animals Name three differences between cancer cells and normal cells Give (a) the type of cells in which you would find a diploid number of chromosomes and a haploid number of chromosomes, and (b) the haploid and diploid numbers of chromosomes in humans Explain why homologous chromosomes are paired Identify where meiosis takes place in animal cells, and what is produced Illustrate spermatogenesis using the chromosome number and number of cells at each division Explain Morgan's findings in fruit flies which led him to describe sex chromosomes A karyotype chart was created, and only one X chromosome was found. Identify the disorder that this represents A karyotype chart was created in which three homologous chromosomes were discovered for chromosome pair number 21. Identify a) the type of disorder, and b) the name of the disorder Name three types of prenatal testing. Problem 132. Complete the following table showing the number of chromosomal DNA molecules and chromosomes for different cells. Use the human chromosome number: diploid, 2n = 46 and haploid, n = 23. Assume one DNA molecule per chromatid Stage # of chromosomal DNA molecules per cell unfertilized egg cell zygote (fertilized egg cell) body cell prior to DNA replication body cell after DNA replication meiotic prophase I cell meiotic I telophase cell meiotic II telophase cell # of chromosomes per cell 133. Medical screening programs are designed to gather information concerning the genetic conditions of individuals. Tests were designed and used to identify individuals who have not sought genetic counselling, but who might be carrying genes responsible for severe genetic disorders. The individuals themselves may not show any of the symptoms of the genetic disorder in question. Critics of the screening programs argue that indiscriminate access to this information could endanger personal freedom. Furthermore, some of these critics claim that there is a right to know, while others claim there is also a right not to know. a) Discuss two possible reasons for individuals wanting to know the results of their own genetic screening. b) Discuss two abuses to which information from genetic screening could contribute Calculate the surface area to volume ratio for: a) Cube 1 - dimensions 2 cm 2 cm 2 cm. SHOW YOUR WORK!

9 b) Cube 2 - dimensions 5 cm (s) 5 cm (s) 5 cm. SHOW YOUR WORK! c) If these cubes represented cells, which Cube represents a problem in terms of surface area to volume ratio? Explain the reason for your answer. Essay 135. The purpose of mitosis is to divide a double set of DNA equally between two daughter cells. Explain the significance of each of the following events with regard to mitosis. a) The chromatin condenses into chromosomes. b) The nucleolus and the nuclear envelope disappear. c) The chromosomes line up at the equator of the cell Colchicine is a plant alkaloid that prevents the assembly of the protein subunits necessary for the formation of spindle fibers. It also inhibits formation of new cell walls. Predict the effects colchicine would have on a cell after it begins mitosis Most homologous chromosomes are not the same at the end of prophase I as they were at the beginning of prophase I. Explain what happens to these chromosomes and how this benefits the species.

10 Cell Division Answer Section TRUE/FALSE 1. ANS: T REF: K/U OBJ: 3.1 LOC: GC ANS: T REF: K/U OBJ: 3.1 LOC: GC ANS: F REF: K/U OBJ: 3.2 LOC: GC ANS: F REF: K/U OBJ: 3.2 LOC: GC ANS: F REF: K/U OBJ: 3.4 LOC: GC ANS: F REF: K/U OBJ: 3.4 LOC: GC ANS: F REF: K/U OBJ: 3.5 LOC: GC ANS: T REF: K/U OBJ: 3.5 LOC: GC ANS: T REF: K/U OBJ: 3.6 LOC: GC ANS: F REF: K/U OBJ: 3.6 LOC: GC ANS: F REF: K/U OBJ: 3.6 LOC: GC ANS: F REF: K/U OBJ: 3.7 LOC: GC ANS: T REF: K/U OBJ: 3.8 LOC: GC ANS: T REF: K/U OBJ: 3.8 LOC: GC ANS: T REF: K/U OBJ: 3.9 LOC: GC1.05 MULTIPLE CHOICE 16. ANS: A REF: K/U OBJ: 3.2 LOC: CG ANS: D REF: K/U OBJ: 3.2 LOC: GC ANS: C REF: I OBJ: 3.2 LOC: GC ANS: E REF: K/U OBJ: 3.2 LOC: GC ANS: D REF: K/U OBJ: 3.2 LOC: GC ANS: E REF: K/U OBJ: 3.2 LOC: GC ANS: B REF: K/U OBJ: 3.2 LOC: GC ANS: A REF: I OBJ: 3.2 LOC: GC ANS: A REF: I OBJ: 3.2 LOC: GC ANS: C REF: I OBJ: 3.2 LOC: GC ANS: B REF: I OBJ: 3.2 LOC: GC ANS: E REF: K/U OBJ: 3.7 LOC: GC1.01, GC ANS: D REF: K/U OBJ: 3.6 LOC: GC ANS: D REF: K/U OBJ: 3.6 LOC: GC ANS: A REF: K/U OBJ: 3.6 LOC: GC ANS: D REF: K/U OBJ: 3.6 LOC: GC ANS: B REF: I OBJ: 3.6 LOC: GC ANS: E REF: K/U OBJ: 3.6 LOC: GC ANS: D REF: K/U OBJ: 3.7 LOC: GC1.04,GC ANS: E REF: K/U OBJ: 3.6, 3.7 LOC: GC1.01, GC ANS: E REF: K/U OBJ: 3.7 LOC: GC1.01, GC ANS: A REF: K/U OBJ: 3.7 LOC: GC1.01, GC ANS: B REF: K/U OBJ: 3.7 LOC: GC1.01, GC1.04

11 39. ANS: D REF: I OBJ: 3.7 LOC: GC ANS: A REF: K/U OBJ: 3.8 LOC: GC ANS: D REF: I OBJ: 3.8 LOC: GC ANS: A REF: K/U OBJ: 3.9 LOC: GC ANS: E REF: I OBJ: 3.9 LOC: GC ANS: C REF: K/U OBJ: 3.9 LOC: GC ANS: C REF: K/U OBJ: 3.2, 3.6, 3.7 LOC: GC1.04, GC ANS: A REF: K/U OBJ: 3.2, 3.6, 3.7 LOC: GC1.01, GC ANS: D REF: K/U OBJ: 3.2, 3.6, 3.7 LOC: GC1.01, GC ANS: B REF: K/U OBJ: 3.6 LOC: GC1.04 COMPLETION 49. ANS: grow, repair REF: K/U OBJ: 3.1 LOC: GC ANS: division, interphase REF: K/U OBJ: 3.2 LOC: GC ANS: cytokinesis REF: K/U OBJ: 3.2 LOC: GC ANS: centromere REF: K/U OBJ: 3.2 LOC: GC ANS: clone REF: K/U OBJ: 3.4 LOC: GC ANS: metastasis REF: K/U OBJ: 3.5 LOC: GC ANS: haploid, diploid REF: K/U OBJ: 3.6, 3.8 LOC: GC ANS: gametes REF: K/U OBJ: 3.6 LOC: GC ANS: Synapsis REF: K/U OBJ: 3.6 LOC: GC ANS: nondisjunction REF: K/U OBJ: 3.9 LOC: GC1.04 MATCHING 59. ANS: E REF: K/U OBJ: 3.5 LOC: GC ANS: B REF: K/U OBJ: 3.2 LOC: GC ANS: D REF: K/U OBJ: 3.2 LOC: GC ANS: G REF: K/U OBJ: 3.6 LOC: GC ANS: H REF: K/U OBJ: 3.6 LOC: GC ANS: A REF: K/U OBJ: 3.1 LOC: GC ANS: F REF: K/U OBJ: 3.6 LOC: GC ANS: I REF: K/U OBJ: 3.6 LOC: GC ANS: C REF: K/U OBJ: 3.2 LOC: GC ANS: J REF: K/U OBJ: 3.6 LOC: GC1.04

12 69. ANS: F REF: K/U OBJ: 3.2 LOC: GC ANS: B REF: K/U OBJ: 3.2 LOC: GC ANS: A REF: K/U OBJ: 3.2 LOC: GC ANS: E REF: K/U OBJ: 3.2 LOC: GC ANS: C REF: K/U OBJ: 3.2 LOC: GC ANS: D REF: K/U OBJ: 3.2 LOC: GC ANS: E REF: K/U OBJ: 3.2 LOC: GC ANS: C REF: K/U OBJ: 3.2 LOC: GC ANS: B REF: K/U OBJ: 3.2 LOC: GC ANS: B REF: K/U OBJ: 3.2 LOC: GC ANS: G REF: K/U OBJ: 3.6 LOC: GC ANS: B REF: K/U OBJ: 3.6 LOC: GC ANS: F REF: K/U OBJ: 3.6 LOC: GC ANS: H REF: K/U OBJ: 3.6 LOC: GC ANS: C REF: K/U OBJ: 3.6 LOC: GC ANS: A REF: K/U OBJ: 3.6 LOC: GC ANS: E REF: K/U OBJ: 3.6 LOC: GC ANS: D REF: K/U OBJ: 3.6 LOC: GC ANS: B REF: K/U OBJ: 3.6 LOC: GC ANS: A REF: K/U OBJ: 3.6 LOC: GC ANS: A REF: K/U OBJ: 3.7 LOC: GC1.01, GC ANS: A REF: K/U OBJ: 3.7 LOC: GC1.01, GC ANS: B REF: K/U OBJ: 3.7 LOC: GC1.01, GC ANS: B REF: K/U OBJ: 3.7 LOC: GC1.01, GC ANS: B REF: K/U OBJ: 3.7 LOC: GC1.01, GC ANS: A REF: K/U OBJ: 3.7 LOC: GC1.01, GC ANS: B REF: K/U OBJ: 3.7 LOC: GC1.01, GC ANS: B REF: K/U OBJ: 3.7 LOC: GC1.01, GC ANS: B REF: K/U OBJ: 3.7 LOC: GC1.01, GC ANS: A REF: K/U OBJ: 3.7 LOC: GC1.01, GC ANS: B REF: K/U OBJ: 3.8 LOC: GC ANS: A REF: K/U OBJ: 3.8 LOC: GC ANS: A REF: K/U OBJ: 3.8 LOC: GC ANS: B REF: K/U OBJ: 3.8 LOC: GC ANS: A REF: K/U OBJ: 3.8 LOC: GC ANS: A REF: K/U OBJ: 3.8 LOC: GC ANS: B REF: K/U OBJ: 3.8 LOC: GC ANS: A REF: K/U OBJ: 3.8 LOC: GC ANS: G REF: K/U OBJ: 3.9 LOC: CG ANS: F REF: K/U OBJ: 3.9 LOC: CG ANS: A REF: K/U OBJ: 3.9 LOC: CG ANS: D REF: K/U OBJ: 3.9 LOC: CG ANS: H REF: K/U OBJ: 3.9 LOC: CG1.04

13 112. ANS: E REF: K/U OBJ: 3.9 LOC: CG ANS: B REF: K/U OBJ: 3.9 LOC: CG ANS: C REF: K/U OBJ: 3.9 LOC: CG1.04 SHORT ANSWER 115. ANS: Meiosis produces haploid male and female gametes, which, following fertilization, restore the normal diploid number of chromosomes in the zygote. If meiosis did not occur, the zygote produced from two 2n gametes would be 4n and would likely not survive. REF: K/U OBJ: 3.6 LOC: GC ANS: Mitosis: No pairing of homologous chromosomes No crossing over of chromatids in prophase Centromere splits in anaphase Chromatids of each chromosome move to opposite poles in anaphase One nuclear division produces two identical diploid cells Meiosis: Homologous chromosomes pair up Crossing-over occurs in prophase I Centromere splits only in anaphase II Homologous chromosomes move to opposite poles in anaphase I Two nuclear divisions produce four different haploid cells REF: K/U OBJ: 3.2, 3.6, 3.7 LOC: GC1.01, GC ANS: The nucleus at the beginning of prophase I has a 2n number of chromosomes, each of which contains two identical chromatids. Meiosis I results in the formation of two haploid cells as each member of a homologous pair of chromosomes moves to the poles of the cell. In meiosis II, the centromere splits and the chromatids (now chromosomes) move to the poles of the cell. Thus, one diploid cell with a DNA equivalent of 4n divides twice to produce four cells each with a DNA equivalent of 1n. REF: I OBJ: 3.6 LOC: GC ANS: Mitosis is the orderly separation of the duplicate sets of a cell's genetic material. Once the separation of the chromosomes is complete, the cell begins cytokinesis, which is the division of the cytoplasm and organelles into two cells. REF: K/U OBJ: 3.1 LOC: GC ANS: Cells divide because of the surface area to volume relationship. An increase in surface area to volume ratio, which occurs as cells divide, rather than an increase in size permits the exchange of nutrients and wastes to take place more easily. REF: I OBJ: 3.1 LOC: GC ANS:

14 a) During the division phase, mitosis and cytokinesis occur. b) During interphase, rapid cell growth, synthesis of DNA for duplication of chromosomes, and growth and preparation for cell division occur. REF: K/U OBJ: 3.2 LOC: GC ANS: a) In an animal cell, a furrow develops, pinching off the cell into two parts. b) In plant cells, the separation is accomplished by a cell plate that forms between the two chromatin masses. The cell plate will eventually develop into a new cell wall, sealing off the contents of the new cells from each other. REF: K/U OBJ: 3.2 LOC: GC ANS: A nucleus is extracted from the cell of one organism and then is introduced into an nucleated cell. The cell is then allowed to develop into an adult. REF: K/U OBJ: 3.4 LOC: GC ANS: Cancer cells divide at rates that far exceed those of their ancestors; they are capable of reproducing in isolation; have the ability to metastasize; they lack the ability to differentiate. REF: K/U OBJ: 3.5 LOC: GC ANS: a) You would find a haploid number of chromosomes in gamete cells and a diploid number of chromosomes in all other cells in the body. b) In humans, the haploid number is 23 and the diploid number is 46. REF: K/U OBJ: 3.6 LOC: GC ANS: Homologous chromosomes are paired chromosomes because they are similar is shape, size, and gene arrangement. REF: K/U OBJ: 3.6 LOC: GC ANS: Meiosis takes place in the testes and ovaries, which produce sperm and egg cells. REF: K/U OBJ: 3.8 LOC: GC ANS: See page 114, Figure 3, of the student text. Students should show 46 chromosomes and one cell initially, followed by two cells each containing 23 chromosomes for the first division, and four cells each containing 23 chromosomes for the second division. REF: K/U OBJ: 3.8 LOC: GC ANS: Morgan discovered that in females, one pair of chromosomes always consisted of two rod-shaped chromosomes of identical length, while the male had one rod-shaped chromosome and a smaller hook-shaped chromosome. REF: K/U OBJ: 3.8 LOC: GC3.01

15 129. ANS: Turner syndrome REF: K/U OBJ: 3.9 LOC: GC ANS: a) This is a trisomic disorder. b) The name of this disorder is Down syndrome. REF: K/U OBJ: 3.9 LOC: GC ANS: Any three of: amniocentesis, karyotyping, chorionic sampling, or multiple marker screen. REF: K/U OBJ: 3.9 LOC: GC1.05 PROBLEM 132. ANS: Stage # of chromosomal DNA # of chromosomes per cell molecules per cell unfertilized egg cell zygote (fertilized egg cell) body cell prior to DNA replication body cell after DNA replication meiotic prophase I cell meiotic I telophase cell meiotic II telophase cell REF: I OBJ: 3.8 LOC: GC ANS: a) Some people might wish to know the results in order to reduce their concerns about the possibility of carrying a gene responsible for a disease that might appear later in the individual's life. This could allow for the person to plan for future situations. Some individuals might decide not to have children in order not to pass possible deleterious genes on to their children. These people might plan to adopt children. b) It is conceivable that some form of compulsory eugenics could be enforced in which the decision to have children might be removed from the individual. Genetic screening might influence insurance companies' decisions, refusing to insure people with possible genetic diseases, in some cases. People could be denied specific types of jobs on the basis of health problems. REF: MC OBJ: 3.9 LOC: GC ANS:

16 a) b) c) Cube 2 would represent a problem because the decreased SA:V ratio would make diffusion and movement of materials into and out of a cell more difficult. There would be less surface area to get materials in. REF: I OBJ: 3.1 LOC: GC1.01 ESSAY 135. ANS: a) Short, condensed chromatin coils (chromosomes) are less likely to get entangled with one another when they line up at the equator and pull apart. b) The nucleolus and nuclear envelope must disappear, so they do not interfere with the movement of the chromosomes. c) Once the chromosomes are lined up at the centre of the cell, they can be attached to spindle fibres, and their separation and movement to the poles can be orderly. REF: I OBJ: 3.2 LOC: GC ANS: If spindle fibres did not form, the chromosomes would remain at the centre of the cell following metaphase. In plant cells, no cell wall would form. In animal cells, however, cytokinesis would occur through the middle of the chromosomes, causing death of the cell. This might make colchicine effective against rapidly dividing cells, such as cancer cells. REF: MC OBJ: 3.2 LOC: GC1.01

17 137. ANS: At the beginning of prophase I, homologous chromosomes pair up and the chromatids often intertwine in a process called crossing over. The chromatid segments break and rejoin to different sections of the homologous chromosomes. This results in a great variety of genetically different gametes being formed by the parent. Thus, offspring formed by the same two parents are likely to be quite different from each other. This genetic diversity within the species increases its chance of survival should environmental conditions change. REF: MC OBJ: 3.6 LOC: GC1.04