MITOSIS & MEOSIS Chap 9-10 - SunsetRidgeMSBiology · MITOSIS & MEOSIS Chap 9-10.1 ... The cell cycle is divided into interphase and ... A c. C b. B d. D ____ 54. Which event during

MITOSIS & MEOSIS Chap 9-10.1

True/False ( 1 point each)

Indicate whether the statement is true or false.

____ 1. Diffusion over large distances is slow and inefficient because it relies on random movement of molecules and

ions.

____ 2. The cell cycle is divided into interphase and mitosis.

____ 3. During prophase in an onion root tip cell, centrioles migrate to the poles of the cell.

____ 4. Stem cells are only of one type: embryonic.

____ 5. Embryonic stem cells are found in various tissues in the body and might be used to maintain and repair the

same kind of tissue in which they are found.

____ 6. A gamete has one-half the number of chromosomes of a regular body cell.

____ 7. Homologous chromosomes are two chromosomes with identical DNA sequences.

____ 8. Recent research suggests that beneficial mutations accumulate faster when species undergo sexual

reproduction rather than asexual reproduction.

____ 9. During meiosis, chromosome number is reduced through three rounds of cell division.

____ 10. Sexual reproduction would be more advantageous than asexual reproduction for organisms living in an

environment that is diverse and undergoes frequent changes.

____ 11. Mendel’s work on garden pea plants resulted in the discovery that genetic traits of parents always blend

together in subsequent generations.

____ 12. In humans, the ability to roll one’s tongue is a dominant trait. Therefore, a tongue roller can only have

children who are also tongue rollers.

____ 13. The separation of genes during crossing over occurs more frequently between genes that are far apart on a

chromosome than for genes that are close together.

____ 14. During meiosis I, homologus chromosome pairs are separated when the centromeres split apart.

____ 15. Meiosis occurs during both sexual reproduction and asexual reproduction.

____ 16. Gregor Mendel’s research supports the idea each organism carries a pair of alleles.

____ 17. In plant cells, cytokinesis begins with a furrow that pinches the cell.

Multiple Choice (2 points each)

Identify the choice that best completes the statement or answers the question.

____ 18. By the end of prophase, each of the following has occurred except ____.

a. tighter coiling of the chromosomes

b. breaking down of the nuclear envelope

c. disappearing of the nucleolus

d. lining up of chromosomes in the cell

____ 19. The chromosomes shown in Figure 9-1 are in which state of mitosis?

Figure 9-1

a. prophase c. anaphase

b. metaphase d. telophase

Figure 9-2

____ 20. Which of the cells depicted in the line graph in Figure 9-2 are most likely cancerous?

a. A c. C

b. B d. D

____ 21. If cancer is present, what is the likely explanation for what happened to the cells depicted in the curves

labeled B and D in Figure 9-2?

a. They thrived with the cancerous cells.

b. They were harmed by radiation therapy.

c. They died off due to natural causes.

d. They died off because the cancerous cells deprived them of nutrients.

____ 22. Which of the following does not occur as a cell grows larger and larger in size?

a. difficulty obtaining nutrients

b. difficulty eliminating wastes

c. ratio of surface area to volume increases

d. diffusion across the cell membrane is impaired

Figure 9-3

____ 23. Which of the graphs in Figure 9-3 shows the correct changes in the amount of DNA in a cell as it moves

through one cell cycle?

a. A c. C

b. B d. D

____ 24. Why is the synthesis stage called this?

a. because protein synthesis is taking place

b. because DNA synthesis is taking place

c. because it combines several smaller stages into one

d. because the chromosomes come together

____ 25. Which of these has occurred by the end of prophase?

a. Sister chromatids are separated.

b. The spindle is beginning to form.

c. The cell membrane has begun to pinch inward.

d. The nuclear membrane has disappeared.

Figure 9-4

____ 26. Figure 9-4 illustrates which stage of mitosis?

a. anaphase c. prophase


____ 27. How is the alignment of chromosomes, shown in Figure 9-4, on the equatorial plate of the cell maintained?

a. They are always located there, since that is where the nucleus was.

b. Tension between opposite spindle fibers pulls them there.

c. The pressure of the cytoplasm moves them there.

d. The chromosomes are attracted to each other and meet there.

____ 28. Which of the following occurs in telophase?

a. chromosomes condense

b. chromosomes line up

c. chromosomes move to opposite poles

d. chromosomes relax

____ 29. A cell has 12 chromosomes. How many chromosomes will each daughter cell have?

a. 4 c. 12

b. 6 d. 24

____ 30. A cell that is undergoing mitosis is examined with a light microscope. An observation that would allow for

identification of the cell as an animal cell rather than a plant cell would be

a. the centrioles migrating.

b. the chromosome pairs separating from each other.

c. the chromosomes twisting about each other.

d. the nucleoli disappearing.

____ 31. The cell cycle is regulated by

a. cyclins c. hormones

b. enzymes d. sugars

____ 32. Cancer cells can reproduce rapidly because they

a. are smaller than normal cells. c. undergo mitosis faster

b. bypass interphase. d. spend less time in interphase

____ 33. What is cancer caused by?

a. cell-membrane damage c. mutation

b. metabolic poisoning d. immune-system damage

____ 34. Prokaryotes divide by binary fission, a form of asexual reproduction in which

a. the nucleus divides into two nuclei.

b. the number of chromosomes in the cell is reduced.

c. a cell divides into two cells with identical genetic information.

d. spindle fibers attach to the poles of the cell.

____ 35. It is often said that normal cells change into cancerous cells frequently in our bodies. Which of the following

explanations accounts for the relative rarity of cancer?

a. The cancerous cells die on their own.

b. The DNA repair system fixes the mutation that causes cancer.

c. The cancer cells grow only very slowly at first.

d. The cancerous cells are normally crowded out by normal cell growth.

____ 36. What is the role of cyclin-dependent kinases in the cell cycle?

a. They stop the cycle if something has gone wrong.

b. They catalyze the condensation of the chromosomes.

c. They provide the energy for the actions of the spindle fibers.

d. They initiate various stages of the cell cycle.

Figure 9-5

____ 37. The cell in Figure 9-5 is undergoing mitosis. Which stage of mitosis will follow this one?

a. anaphase c. prophase


____ 38. Which checkpoint has this cell just passed?

a. near the end of gap 1, monitoring DNA damage

b. during the S stage

c. during the gap 2 stage

d. during mitosis, monitoring spindle formation

____ 39. DNA replication occurs during

a. anaphase. c. metaphase.

b. interphase. d. prophase.

____ 40. If you were studying the causes of cancer, which topic might interest you?

a. cyclin-dependent kinases c. spindle-fiber structure

b. centromere structure d. cell membranes

____ 41. Which of the phases of mitosis has the shortest duration?

a. anaphase c. metaphase

b. cytokinesis d. prophase

____ 42. A cell that undergoes repeated mitosis without cytokinesis would have

a. many daughter cells. c. many nuclei.

b. fewer chromosomes. d. cancerous properties.

____ 43. Why is it important for the chromosomes to condense during mitosis?

a. to facilitate DNA replication

b. to facilitate chromosome movement

c. to facilitate cytokinesis

d. to facilitate spindle formation

____ 44. The typical growth period of a cell occurs during which stage of the cell cycle?

a. Gap 1 c. synthesis

b. Gap 2 d. mitosis

____ 45. Some cancers have a genetic component to them, if a parent has a cancer the children are more likely than the

average population to develop the cancer. Why might this be?

a. Cancers require more than one mutation to occur.

b. Cancers are inherited but remain dormant until a certain age.

c. Parents and children are often exposed to similar environmental factors.

d. Cancers are often recessive traits and require alleles from both parents.

____ 46. Colchicine is a chemical that when applied to a cell during mitosis can be used to “freeze” cells in metaphase

by preventing the chromosomes from moving away from the metaphase plate. What part of the cell does

colchicine most likely affect?

a. chromosome structure c. nuclear membrane

b. spindle fibers d. cell membrane

____ 47. A stem cell has potential medical uses because it

a. undergoes mitosis.

b. is not specialized in structure and function.

c. is similar to a cancer cell, providing a study system.

d. undergoes apoptosis.

____ 48. The numbers in Figure 10-1 represent the chromosome number found in each of the dog cells shown. The

processes that are occurring at A and B are ____.

Figure 10-1

a. mitosis and fertilization c. mitosis and pollination

b. meiosis and fertilization d. meiosis and pollination

____ 49. A white mouse whose parents are both white produces only brown offspring when mated with a brown

mouse. The white mouse is most probably ____.

a. homozygous recessive c. homozygous dominant

b. heterozygous d. haploid

____ 50. The diagram in Figure 10-2 shows a diploid cell with two homologous pairs of chromosomes. Due to

independent assortment, the possible allelic combinations that could be found in gametes produced by the

meiotic division of this cell are ____.

Figure 10-2

a. Bb, Dd, BB, and DD c. BbDd and BDbd

b. BD, bD, Bd, and bd d. Bd and bD only

____ 51. Using Figure 10-3, which process would result in the formation of chromosome C from chromosomes A and

B?

Figure 10-3

a. asexual reproduction c. crossing over

b. independent assortment d. segregation

Figure 10-8

____ 52. In Figure 10-8, which set of chromatids illustrates the result of a single crossover of the homologous

chromosomes?

a. A c. C

b. B d. D

____ 53. In Figure 10-8, which set of chromatids will result if each chromatid crossed with a nonsister chromatid?

a. A c. C

b. B d. D

____ 54. Which event during meiosis leads to a reduction in chromosome number from 2n to n?

a. Pairs of homologous chromosomes line up at the equator.

b. DNA undergoes replication.

c. Homologous chromosomes travel to opposite sides of the cell.

d. Sister chromatids are pulled apart at the centromere.

____ 55. Crossing over would most likely occur during which stage of the cell cycle?

a. when DNA is being replicated

b. when homologous chromomosomes line up in pairs

c. when centromeres are separated

d. when cytokinesis begins

____ 56. Which is the best description of the events that take place during anaphase II?

a. The replicated chromosomes become visible.

b. Homologous chromosomes line up along the equator.

c. Sister chromatids are separated and pulled to opposite sides of the cell.

d. Homologous pairs are separated and pulled to opposite sides of the cell.

____ 57. What is the role of the spindle fibers?

a. to join homologous chromosomes together

b. to store nucleotides prior to DNA synthesis

c. to initiate the formation of the nuclear membrane

d. to move chromosomes in the cell

____ 58. The typical human body cell contains 46 chromosomes. How many chromosomes are found in a typical

human sperm?

a. 23 c. 46

b. 45 d. 92

____ 59. Suppose an animal is heterozygous AaBb, and the traits are not linked. When meiosis occurs, what is the total

number of possible combinations of gametes that can be made for these traits?

a. 2 c. 6

b. 4 d. 8

____ 60. Suppose an animal is heterozygous AaBbCc, and the traits are not linked. When meiosis occurs, what is the

total number of possible combinations of gametes that can be made for these traits?

a. 3 c. 8

b. 6 d. 12

____ 61. During which phase of meiosis do homologous pairs of chromosomes line up next to one another along the

equator?

a. anaphase I c. prophase II

b. metaphase I d. metaphase II

____ 62. Which stage of meiosis is responsible for the law of independent assortment?

a. metaphase I c. telophase I

b. prophase I d. metaphase II

____ 63. A true-breeding tall pea plant is crossed with a true-breeding short pea plant, and all the offspring are tall.

What is the most likely genotype of the offspring assuming a single-gene trait?

a. tt c. TT

b. Tt d. TT or tt

____ 64. Mendel took the pollen from a tall pea plant and pollinated the flower of a short pea plant. When he did this,

he removed the male parts of the flower on the short plant. Why was it important that he remove the male

parts from the flower of the short plant?

a. because he wanted to prevent self pollination

b. because the short plant was heterozygous

c. because he wanted to prevent the development of seeds

d. because the short plant was not a true-breeding plant

____ 65. A heterozygous organism is best described as which of these?

a. dominant c. hybrid

b. genotype d. true-breeding

Figure 10-9

____ 66. Consider the cell labeled X in Figure 10-9 containing 4 chromosomes. Which of the four cells below it

represents a healthy gamete that could be produced from this cell?

a. A c. C

b. B d. D

Figure 10-10

____ 67. Which stage of meiosis is represented in Figure 10-10?

a. anaphase I c. anaphase II

b. metaphase I d. metaphase II

Completion ( 1 point each)

Complete each statement.

68. Mitosis is the division of ____________________.

69. Cytokinesis is division of the _____________________.

70. If cells do not respond to the normal mechanisms that control cell division, ____________________ results.

71. ____________________ are unspecialized cells that can develop into specialized cells under the right

conditions.

72. An individual with the genotype Aa is ____________________ for the trait.

73. Genes on separate chromosomes follow Mendel’s law of ____________________.

74. The possible combination of genes in any gamete due to independent assortment equals 2

n, where n equals the

number of ____________________.

75. The term ____________________ refers to the occurrence of one or more sets of extra chromosomes in an

organism.

76. Interphase is divided into three stages: G1, ____________________, and G2.

77. The longest stage of mitosis is ____________________.

78. Once the cell cycle begins, there are built-in ____________________ that can stop it at any time.

79. During development some cells go through a programmed cell death called ____________________.

Short Answer ( 4 points each)

The large size of many fruits and flowers is the result of polyploidy, a condition in which the nuclei of an

organism's cells contain extra sets of chromosomes. Polyploidy often occurs naturally, but it can also be

artificially induced by plant breeders. How have breeders been able to mimic a naturally occurring

phenomenon?

Researchers have determined that the chemical colchicine suppresses cell division by preventing the

formation of spindle fibers. Without these fibers, the sister chromatids cannot become properly oriented for

separation into individual nuclei. In effect, mitosis is stopped after prophase. However, the cell may continue

to make copies of its chromosomes. As a result, the nucleus of the cell contains multiple sets of

chromosomes.

Suppose a researcher wished to investigate how extra sets of chromosomes are produced. First, she treated

two onion roots with a colchicine solution and left two roots untreated. After a period of several days, she

placed thin slices from each root tip on separate slides, stained the specimens, and examined the slides under a

microscope at high power.

80. How do you predict the slides of treated and untreated root tips will differ?

81. If the researcher finds only cells in interphase and prophase in the slides of treated root tips, what might be her

interpretation?

82. Describe what happens in each stage of interphase.

83. How does meiosis maintain a constant number of chromosomes in the body cells of organisms that reproduce

sexually?

Figure 9-6

84. Cells A and F of Figure 9-6 show an early and a late stage of the same phase of mitosis. What phase is it?

85. How does a high ratio of surface area to volume benefit a cell?

Essay: Choose only 1 to answer (10 points) Please be thorough in your essay so that all points may be awarded to

you.

86. During cell division, two genetically identical daughter cells are produced from a single cell. Describe the

occurrences relating to the chromosomes during the entire cell cycle, specifically pointing out the steps that

lead to genetic identity of the daughter cells.

87. Explain the roles of environment and genetics in causing cancer.

MITOSIS & MEOSIS Chap 9-10.1

Answer Section

TRUE/FALSE

1. ANS: T

Movement of substances in a cell is more easily managed if the cell is small.

PTS: 1 DIF: Bloom's Level C REF: 245

TOP: 9-1

2. ANS: F

The cell cycle has three stages: interphase, mitosis, and cytokinesis.

PTS: 1 DIF: Bloom's Level A REF: 246

NAT: LS_1d TOP: 9-2

3. ANS: F

Centrioles are not present in plant cells. Only spindle fibers are present.

PTS: 1 DIF: Bloom's Level D REF: 250

NAT: LS_1d TOP: 9-4

4. ANS: F

There are two basic types of stem cells: embryonic and adult.

PTS: 1 DIF: Bloom's Level B REF: 256

NAT: LS_1f TOP: 9-9

5. ANS: F

Embryonic stem cells are unspecialized cells. They have the capability of developing into a wide variety of

specialized cells. Adult stem cells are found in various tissues of the body and used to repair the tissue in

which they are found.

PTS: 1 DIF: Bloom's Level B NAT: LS_1f

TOP: 257

6. ANS: T

During meiosis, the number of chromosomes is reduced to one-half the original number.


NAT: LS_2b TOP: 10-1

7. ANS: F

Homologous chromosomes contain the same genes as one another, but the DNA sequences vary. One

homolog comes from an individual’s father, while the other comes from the mother.


NAT: LS_2a TOP: 10-3

8. ANS: T

Sexual reproduction allows for more variety in offspring, allowing natural selection to play a stronger role in

favoring those individuals with beneficial traits.



9. ANS: F

Only two rounds occur.



10. ANS: T

Sexual reproduction allows for greater variety in offspring. Thus, in a variable and diverse environment, there

is a greater chance of success for organisms that reproduce sexually as compared to organisms that reproduce

asexually.



11. ANS: F

He discovered that traits were discrete and could be “hidden” by other traits, but could reappear in another

generation in their original form.

PTS: 1 DIF: Bloom's Level B REF: 277–279


12. ANS: F

This statement would only be true if the tongue roller was homozygous (TT). If the tongue roller is

heterozygous (Tt) and has children with someone else that carries the t allele, then it is possible for them to

have a child who cannot roll his or her tongue.

PTS: 1 DIF: Bloom's Level D REF: 279–281


13. ANS: T

The farther apart two loci are, the more likely it is that they will be separated by a crossover.



14. ANS: F

Homologous chromosomes separate, but centromeres do not.

PTS: 1 DIF: Bloom's Level A REF: 270–275


15. ANS: F

Meiosis occurs in sexual reproduction only.



16. ANS: T

He concluded the genes come in pairs, such as round versus smooth seed, or green versus yellow seed.



17. ANS: F

Plants have a rigid cell wall that covers their plasma membrane. Therefore, they must form a new structure

called a cell plate between the daughter cells.


NAT: LS_1d TOP: 9-5

MULTIPLE CHOICE

18. ANS: D

In prophase, the cell’s chromatin tightens into chromosomes. Near the end of this stage, the nuclear envelope

breaks down and disappears. Finally, the spindle starts to form.

Feedback

A See page 248 for help. B Good try. C That occurs during prophase. D That's correct!


NAT: LS_1d TOP: 9-4

19. ANS: C

In anaphase, the chromatids are pulled apart. The microtubules of the spindle apparatus begin to shorten,

which pulls the centromere and breaks it. This causes the sister chromatids to separate.

Feedback

A Prophase is an earlier stage. B Try again C That's correct! D No, telophase is the final stage before cell division.


NAT: LS_1d TOP: 9-4

20. ANS: A

Cancer is the uncontrolled growth and division of cells.

Feedback

A That's correct! B No, the number of cells is going down. C Try again. D Did you consider all the factors?


NAT: LS_1d TOP: 9-7

21. ANS: D

When unchecked, cancer cells can kill an organism by crowding out normal cells, resulting in loss of tissue

function.

Feedback

A Look at the graph again. B Try again. C See page 254 for help. D That's correct!

PTS: 1 DIF: Bloom's Level E REF: 254

NAT: LS_1d TOP: 9-7

22. ANS: C

If a cell continues to grow, the ratio of surface area to volume will decrease. This means the cell will have

difficulty supplying nutrients and expelling enough waste products. Diffusion across the cell membrane will

not be affected.

Feedback

A Try again. B Did you consider all the factors? C That's correct! D See page 245 for help.


NAT: LS_1d TOP: 9-1

23. ANS: B

The amount of DNA doubles during the S phase and is then halved after cytokinesis.

Feedback

A Does the DNA increase four times at any point? B Do you end up with half the amount of DNA you started with as shown? C That's right! D The amount of DNA does change with time during the cell cycle.


NAT: LS_1d TOP: 9-2

24. ANS: B

“Synthesis” refers to the synthesis of DNA during this phase.

Feedback

A This is not what is being made. B That's correct! C It refers to something being made. D Review the material on page 247.


NAT: LS_1d TOP: 9-3

25. ANS: D

By the end of prophase the nuclear membrane has disintegrated.

Feedback

A This occurs during anaphase. B This occurs at the beginning of prophase. C This occurs in telophase. D That's right!


NAT: LS_1d TOP: 9-4

26. ANS: B

During metaphase, the spindle apparatus aligns the sister chromatids in the center, or equator, of the cell.

Feedback

A Try again. B That's correct! C See page 250 for help. D Look at what the chromosomes are doing.


NAT: LS_1d TOP: 9-4

27. ANS: B

Each chromosome is attached to opposing spindle fibers at the centromere. These spindle fibers can grow or

shrink and pull the chromosomes to the equatorial plate by maintaining tension in opposite directions.

Feedback

A The nucleus is not always at the center of the cell. B That's right! C See page 250 for help. D See page 250 for help.

PTS: 1 DIF: Bloom's Level F REF: 250

NAT: LS_1d TOP: 9-4

28. ANS: D

In telophase, the chromosomes arrive at the poles and begin to relax, or decondense.

Feedback

A That's prophase. B That's metaphase. C That's anaphase. D That's correct!


NAT: LS_1d TOP: 9-4

29. ANS: C

During mitosis, the cell’s replicated genetic material separates and the cell prepares to divide into two cells.

Feedback

A Did you consider all the factors? B Too low. This would occur in meiosis. C That's correct! D That's too many.


NAT: LS_1d TOP: 9-4

30. ANS: A

All of the events can happen in both plant and animal cells except choice A. Plant cells do not have

centrioles.

Feedback

A That's correct! B Try again. C See page 250 for help. D Both plant and animal cells have nucleoli.


NAT: LS_1d TOP: 9-4

31. ANS: A

The normal cell cycle is regulated by cyclin proteins.

Feedback

A That's correct! B Good try. C Try again. D See page 253 for help.


NAT: LS_1d TOP: 9-6

32. ANS: D

Cancer cells spend less time in interphase than do normal cells.

Feedback

A Try again. B See page 254 for further information. C Mitosis takes as long in cancer cells. D That's correct!


NAT: LS_1d TOP: 9-7

33. ANS: C

Cancer can have diverse causes, all of which result in mutation in a cell’s DNA.

Feedback

A This will just kill a cell. B This doesn't cause cancer. C That's right! D Have a look at page 254.


NAT: LS_1d TOP: 9-7

34. ANS: C

When prokaryotic DNA is duplicated, both copies attach to the plasma membrane. As the plasma membrane

grows, the attached DNA molecules are pulled apart. The cell completes fission, producing two new

prokaryotic cells.

Feedback

A See page 252 for help. B Try again.

C That's correct! D Did you consider all the factors?


NAT: LS_1d TOP: 9-5

35. ANS: B

The mutations that might lead to cancer occur relatively frequently but DNA repair systems correct them.

Cancer often is a result of a mutation in the DNA repair system itself that prevents it from fixing other

mutations.

Feedback

A If they are cancerous they won't die. B That's right! C Think about what causes cancer. D The opposite is what happens with cancer cells.


NAT: LS_1d TOP: 9-7

36. ANS: D

The cyclin-dependent kinases initiate various phases of the cell cycle such as the synthesis phase.

Feedback

A This is the role of the cycle checkpoints. B Have a look on page 253. C This is not their role. D That's right!


NAT: LS_1d TOP: 9-6

37. ANS: B

In this stage, the chromosomes are condensing and the spindle is beginning to form. Therefore, this stage is

prophase. The one to follow it is metaphase.

Feedback

A That's a later stage. B That's correct! C This cell is currently in prophase. D Try again.

PTS: 1 DIF: Bloom's Level C REF: 248–250

NAT: LS_1d TOP: 9-4

38. ANS: C

This cell has recently left the gap 2 stage and has therefore passed the checkpoint near the end of that stage.

Feedback

A See page 254 for more information. B Which stage is this cell in? C That's correct! D The spindle has not completely formed yet.


NAT: LS_1d TOP: 9-6

39. ANS: B

During the second stage of interphase, called synthesis, a cell copies its DNA in preparation for cell division.

Feedback

A DNA replication has already occurred by this point. B That's correct! C See page 247 for help. D Try again.


NAT: LS_1d TOP: 9-3

40. ANS: A

One of the causes of cancer is mutations in the proteins that regulate the cell cycle, some of which are

cyclin-dependent kinases. These enzymes would be a useful place to begin understanding the causes of

cancer.

Feedback

A That's correct! B The centromere is involved in proper movement of the chromosomes, not cancer. C Are the spindle fibers involved in cancer? D See pages 253–254 for further help.


NAT: LS_1d TOP: 9-7

41. ANS: C

Metaphase is one of the shortest stages of mitosis, but when completed successfully, it ensures that new cells

have accurate copies of the chromosomes.

Feedback

A Good guess! B That's not part of mitosis. C That's correct! D That's the longest phase!


NAT: LS_1d TOP: 9-4

42. ANS: C

Mitosis is the division of the nucleus. Without cytokinesis, or cell division, mitosis alone will lead to a

multinucleate cell. This occurs in many organisms, especially fungi.

Feedback

A Cytokinesis is what produces the daughter cells. B The chromosome numbers would not decrease. C That's right! D Cancer is a result of uncontrolled cell division; in this case division is not occurring.


NAT: LS_1d TOP: 9-2

43. ANS: B

The decondensed chromosomes are so long and diffuse that they could not be disentangled when they are

dragged to the poles of the dividing cell.

Feedback

A You're not considering when condensation takes place. B That's right! C The chromosomes aren't involved in cytokinesis. D The chromosomes aren't involved in spindle formation.


NAT: LS_1d TOP: 9-4

44. ANS: A

The normal growth of the cell occurs in Gap 1 before the chromosomes are replicated.

Feedback

A That's correct! B This is after synthesis, does that make sense? C The cell is busy replicating DNA during this period. D Have a look at page 247.


NAT: LS_1d TOP: 9-2

45. ANS: A

Cancers are often caused by multiple mutations, inheriting one mutation from a parent means the individual

has to develop fewer mutations to develop the cancer.

Feedback

A That's correct! B This is not how it works. C But this isn't genetic. D This isn't the case; think about how mutations contribute to cancer.


NAT: LS_1d TOP: 9-7

46. ANS: B

Colchicine inhibits the formation of the microtubules or spindle fibers. Without the spindle fibers the

chromosomes cannot move to the poles.

Feedback

A The movement of chromosomes isn't directly affected by their structure. B That's right! C The nuclear membrane isn't present at this stage. D The nuclear membrane doesn't affect chromosome movement.

PTS: 1 DIF: Bloom's Level E REF: 250–251

NAT: LS_1d TOP: 9-4

47. ANS: B

A stem cell’s usefulness lies in the fact that it is unspecialized and therefore has the potential to develop into

cells of different kinds that might be used to repair damaged tissue.

Feedback

A Many cells undergo mitosis; this is not their usefulness. B That's right! C They are not especially similar to cancer cells. D This is not their usefulness.


NAT: LS_1f TOP: 9-9

48. ANS: B

Meiosis involves the reduction in chromosome number prior to fertilization.

Feedback

A If this were mitosis, then step A would not lead to a reduction in chromosome number. B Correct. C Pollination occurs in plants. D Pollination occurs in plants.



49. ANS: A

The most likely scenario is that the white mouse displays the recessive trait. If this is the case, then the white

mouse must be homozygous. If the white mouse were either homozygous dominant or heterozygous, then it

would likely produce white offspring when mated with a brown mouse.

Feedback

A Correct. B If the white mouse is heterozygous, then this would mean white is dominant and its

brown mate is homozygous recessive. Such a cross would yield about half white and

brown offspring. C If the white mouse were homozygous dominant, then its offspring would have to be

white. D Sperm and eggs are haploid. Individual mice are not.



50. ANS: B

Chromosomes separate so that one of each gamete contains one member of each pair. Thus, B and b would

not be found together, nor would D and d. However B can be combined with either D or d, and similarly b can

be combined with either D or d.

Feedback

A Homologous pairs would separate from one another. B Correct. C Each gamete would have one copy of each homologous pair. D Four combinations are possible.



51. ANS: C

Crossing over leads to new combinations of alleles on a given chromomosome.

Feedback

A Asexual reproduction does not lead to new combinations of alleles. B Review independent assortment. C Correct. D Check page 272.



52. ANS: A

A single crossover will cause B and b to change positions relative to A and a on just two chromatids. The

other two chromatids will be unaffected, one would remain AB and the other aa. The chromatids that

experience the crossover will contain Ab and aB.

Feedback

A This is correct. B This shows the effect of zero crossovers. C This shows the effect of two crossovers. D There should be 2 copies of B.



53. ANS: C

This would result in recombination on all the chromatids, producing two Ab chromatids and two aB

chromatids.

Feedback

A This is the result of one crossover. B Try again. C Correct. D There must be two B alleles.



54. ANS: C

Reduction in chromosome number occurs when homologous pairs of chromosomes are separated during

meiosis I.

Feedback

A The cell is still 2n at this point. B Check page 272. C Correct. D The cells are already n at this point.



55. ANS: B

Crossing over refers to the exchange of DNA, which occurs when homologous chromosomes form pairs.

Feedback

A Check page 272. B Well done. C Crossing over occurs before this. D Try again.



56. ANS: C

Anaphase is the phase in which chromosomes are separated. Homologous pairs are separated during anaphase

I. Sister chromatids are separated during anaphase II.

Feedback

A This is prophase I. B This is metaphase I. C This is correct. D This is anaphase I.



57. ANS: D

Spindle fibers attach to centromeres and move chromosomes.

Feedback

A See pages 272 and 274. B See pages 272 and 274. C Spindle fibers attach to chromosomes. D Correct.



58. ANS: A

The sperm contains half the number of chromosomes found in a body cell.

Feedback

A Correct. B Sperm contain a haploid number of chromosomes. C A body cell has twice the number of chromosomes as a sperm. D See pages 272–274.



59. ANS: B

There are four combinations: AB, Ab, aB, and ab.

Feedback

A Remember the traits are not linked. B Correct. C Check page 275. D Find all possible combinations of A with B and b and a with B and b.



60. ANS: C

Each of the following 8 combinations are possible: ABC, ABc, AbC, aBC, Abc, aBc, abC, and abc.

Feedback

A Remember that the traits assort independently. B Consider all possible combinations of the three alleles. C Well done. D There are 2 x 2 x 2 possible combinations.



61. ANS: B

Homologous pairs line up along the equator of the cell during metaphase I.

Feedback

A This is when homologous pairs move away from each other. B Correct. C See page 275. D Homologous pairs are separated before meiosis II.



62. ANS: A

The arrangement of alleles in the gametes is determined by the way the homologous pairs line up at the

equator during metaphase I.

Feedback

A Well done. B Chromosomes are condensing, but have not yet lined up on the equator. C See page 275. D Homologous pairs were already separated before this stage.



63. ANS: B

Since the parents are true breeding, they are most likely homozygous (TT and tt). This means the offspring are

most likely heterozygous, Tt.

Feedback

A See page 280.

B Correct. C But one parent was short. D If all offspring are tall, then they cannot be TT and tt.



64. ANS: A

He removed the male parts on the short plant because he wanted to avoid letting the plant self-pollinate. He

wanted the pollen to come only from a tall plant.

Feedback

A Correct B Both plants were true-breeding homozygous. C Mendel used the seeds. D Mendel used only true-breeding plants.


NAT: IS_1a TOP: 10-4

65. ANS: C

A heterozygous (Aa) individual is produced by a cross of two different true-breeding (AA and aa)

individuals.Thus the heterozgous individual is a hybrid.

Feedback

A This description refers to a trait or allele. B This description refers to the genetic makeup of an individual. C Correct. D This refers to a homozygous individual.



66. ANS: A

The healthy gamete would have half the original number of chromatids. In this case, the number is A.

Feedback

A Correct. B The chromatids in the gamete would not be joined at the centromere. C There should be two chromatids in the gamete. D Try again.



67. ANS: D

Chromosomes line up at the equator of the cell during metaphase II.

Feedback

A The chromosomes are lined up along the equator. B The chromosomes are not in pairs. C Check page 275. D Correct.



COMPLETION

68. ANS: a nucleus


NAT: LS_1d TOP: 9-2

69. ANS: cytoplasm


NAT: LS_1d TOP: 9-5

70. ANS: cancer


NAT: LS_1d TOP: 9-7

71. ANS: Stem cells


NAT: LS_1f TOP: 9-9

72. ANS: heterozygous



73. ANS: independent assortment



74. ANS: chromosome pairs



75. ANS: polyploidy


NAT: LS_2c TOP: 10-9

76. ANS: synthesis


NAT: LS_1d TOP: 9-3

77. ANS: prophase


NAT: LS_1d TOP: 9-4

78. ANS: checkpoints


NAT: LS_1d TOP: 9-6

79. ANS: apoptosis


NAT: LS_1f TOP: 9-8

SHORT ANSWER

80. ANS:

Answers may vary. The slides of untreated root tips will show cells in interphase and in various stages of

mitosis. The slides of treated root tips will show cells only in interphase and in prophase, and they may show

some cells with multiple sets of chromosomes.


NAT: LS_1d TOP: 9-6

81. ANS:

The colchicine stopped mitosis after prophase.


NAT: LS_1d TOP: 9-6

82. ANS:

During G1, a cell is growing, carrying out normal functions, and preparing to replicate its DNA. During

synthesis, the cell copies its DNA in preparation for mitosis. Finally, G2 is the stage in which the cell

prepares for division of the nucleus.


NAT: LS_1d TOP: 9-3

83. ANS:

Meiosis reduces the number of chromosomes to n or half in the sperm and egg. When fertilization occurs, the

2n number of chromosomes is restored.



84. ANS:

prophase


NAT: LS_1d TOP: 9-4

85. ANS:

Answers will vary. A smaller cell can more efficiently transport substances. In addition, wastes will be

expelled more effectively and it will be easier to obtain nutrients. For the cytoskeleton to be an efficient

transportation mechanism, the cell must be small.


TOP: 9-1

ESSAY

86. ANS:

During interphase the chromosomes are decondensed, existing as diffuse strands of DNA and protein. During

the synthesis stage of interphase each of the chromosomes is duplicated and the two replicated, and identical,

strands remain attached to each other. During prophase of mitosis the chromosomes begin to condense until

they form compact bodies that consist of the two identical sister chromatids (containing identical copies of

DNA) joined at the centromere. With the formation of the spindle apparatus, spindle fibers attach from

opposing poles to the centromeres of each chromsome. The spindle fibers position the chromsomes on the

equatorial plate by metaphase. During anaphase the centromeres separate and spindle fibers pull each sister

chromatid of a chromosome to an opposite pole. This precise separation of the two halves of each

chromosome is what ensures that each daughter cell will receive the exact same genetic material. As telophase

proceeds, the chromosomes begin to decondense and the nuclear membrane forms around them again.

Cytokinesis partitions the two sets of nuclear material into the two daughter cells.


NAT: LS_1d TOP: 9-2 | 9-4

87. ANS:

All cancers are caused by genetic changes in cells. These changes are mutations in genes that control the cell

cycle, or changes in genes that control DNA repair and therefore make it easier for other mutations to occur.

The causes of the mutations are environmental. Certain substances such as asbestos are able to cause

mutations in DNA and some of these mutations may lead to cancer. Cancers often show trends in families.

This is because it takes several mutations before cancer is caused. If an individual inherits one of the

mutations from a parent, then that individual is more likely to develop the cancer by developing the fewer

extra necessary mutations.


NAT: LS_1d TOP: 9-7

Documents

MITOSIS & MEOSIS Chap 9-10 - SunsetRidgeMSBiology · MITOSIS & MEOSIS Chap 9-10.1 ... The cell cycle is divided into interphase and ... A c. C b. B d. D ____ 54. Which event during