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Biology Exam 3 > Chapter 12 > Flashcards

Chapter 12 Flashcards

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1
Q

Why do unicellular organisms undergo cell division?

A

to reproduce

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2
Q

Why do multicellular organisms undergo cell division?

A

depend on cell division for development, growth, and repair

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3
Q

Somatic cells

A

(non reproductive cells) have two sets of chromosomes (diploid, 2n)

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4
Q

Gametes

A

(reproductive cells: sperm and eggs) have half as many chromosomes as somatic cells (haploid, n)

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5
Q

Why are the terms “n” and “2n” used to symbolize haploid and diploid?

A

n is the number of chromosomes. 2n means that there’s 2 sets of chromosomes.

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6
Q

If 2n = 6, then what does n equal?

A

n = 3

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7
Q

Homologous chromosome pairs

A

a pair of two chromosomes that have the same length, shape, and carry genes controlling the same characters.

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8
Q

What are the two phases of the cell cycle?

A

Interphase and mitotic (M) phase

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9
Q

During which of these phases does the cell spend 90% of its time?

A

interphase

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10
Q

What is the mitotic phase?

A

mitosis and cytokinesis

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11
Q

What is interphase?

A

cell growth and copying of chromosomes in preparation for cell division

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12
Q

What is mitosis?

A

Division of the nucleus to produce two genetically identical daughter cells

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13
Q

What is cytokinesis?

A

the division of the cytoplasm.

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14
Q

What is the relationship between mitosis and cytokinesis?

A

Cytokinesis overlaps mitosis in the telophase stage

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15
Q

Name the three phases of Interphase.

A

G1 phase, S phase, and G2 phase

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16
Q

What occurs during the G1 phase of interphase

A

First gap; cell growth occurs

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17
Q

What occurs during the S phase of interphase

A

DNA replication occurs

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18
Q

What occurs during the G2 phase of interphase

A

Second gap; cell growth & centrosome replication occurs

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19
Q

Describe the chromosomes before the S phase of interphase

A

Before the S phase, chromosomes only have one DNA molecule.

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20
Q

Describe the chromosomes during the S phase of interphase

A

During the S phase, the cell copies the DNA molecules of each chromosome.

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21
Q

Describe the chromosomes after the S phase of interphase

A

After S phase, chromosomes have two chromatids meaning each chromosome has two molecules of DNA.

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22
Q

Prophase

A

the chromosomes are located inside the nuclear envelope, are still in their replicated form, and the mitotic spindle is just starting to form

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23
Q

Metaphase

A

The chromosomes are all lined up at the metaphase plate, an imaginary plate at the midway point between the spindle’s two poles

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24
Q

Anaphase

A

Sister chromatids separate and move along the kinetochore microtubules toward opposite ends of the cell. The microtubules shorten by depolymerizing at their kinetochore ends. Nonkinetochore microtubules from opposite poles overlap and push against each other, elongating the cell.

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25
Q

Telophase & cytokinesis

A

nuclear envelope reforms, the unreplicated chromosomes decondensed, cytoplasm
divides, a cleavage furrow forms and grows along the metaphase plate, microfilaments tighten at the
metaphase plate splitting the cell into two causing the formation of two daughter cells

26
Q

Cytokinesis

A

Cytokinesis begins during anaphase or telophase and the spindle eventually disassembles

27
Q

Function of kinetochore

A

Kinetochores serve as a bridge between the DNA of a chromosome and nonkinetochore microtubules

28
Q

Function of nonkinetochore

A

Polymers that work with kinetochores to align and separate chromosomes. Responsible for elongating the cell during anaphase.

29
Q

How does cytokinesis occur in animal cells

A

In animal cells, cytokinesis occurs by a process known as cleavage, forming a cleavage furrow.

30
Q

How does cytokinesis occur in plant cells

A

In plant cells, a cell plate forms during cytokinesis.

31
Q

During which phases of the cell cycle are the chromosomes single?

A

G1 interphase, anaphase, telophase, cytokinesis

32
Q

During which phases of the cell cycle are the chromosomes replicating?

A

S phase interphase

33
Q

During which phases of the cell cycle are the chromosomes replicated?

A

G2 interphase, prophase, prometaphase, metaphase

34
Q

Do prokaryotes undergo mitosis?

A

No, they reproduce by a type of cell division called binary fission.

35
Q

Binary fission steps

A

1) the chromosome replicates (beginning at the origin of replication)
2) the two daughter chromosomes actively move apart
3) The plasma membrane pinches inward
4) cell divides into two

36
Q

What are cell cycle checkpoints?

A

The sequential events of the cell cycle are directed by a distinct cell control system, which is similar to a clock. The cell cycle control system is regulated by internal and external controls.

37
Q

When do checkpoints occur during the cell cycle?

A

The clock has specific checkpoints where the cell cycle stops until a go-ahead signal is received.

38
Q

What happens if the cell receives the go signal at the G1 checkpoint?

A

it will usually complete the S, G2, and M phases and divide.

39
Q

What happens if the cell receives the stop signal at the G1 checkpoint?

A

it will exit the cycle, switching into a non-dividing state called the G0 phase

40
Q

How is the cell cycle checkpoint during mitosis controlled?

A

The cell cycle is controlled at three checkpoints.

G1 checkpoint:
- integrity of the DNA is assessed

G2 checkpoint:
- Proper chromosome duplication is assessed

M Checkpoint:
- Attachment of each kinetochore to a spindle fiber is assessed

41
Q

Anchorage dependence

A

means that the cell needs to be attached to something in order to divide.

42
Q

Density dependence

A

means that the cell won’t divide if it is completely surrounded by other cells. In order for division to be triggered, some of the surrounding cells need to be removed.

43
Q

How might mutation in the genes that control anchorage dependence and density dependence lead to cancer?

A

If density dependence fails, the cells will continue to divide unnecessarily causing a tumor. If anchorage dependence fails, the cells may be able to survive and divide after breaking off from the original tumor leading to cancer cells spreading.

44
Q

Daughter cell

A

the cells that are produced as a result of mitosis. These cells are identical to each other, and also to the original parent cell.

45
Q

gametes

A

Sex cells (sperm and egg)

46
Q

aster

A

a radial array of short microtubules that extends from each centrosome toward the plasma membrane in an animal cell undergoing mitosis.

47
Q

chromatin

A

granular material visible within the nucleus; consists of DNA tightly coiled around proteins

48
Q

nuclear envelope

A

double membrane perforated with pores that control the flow of materials in and out of the nucleus.

49
Q

nuclear envelope fragmentation

A

allowing the extending microtubules to come into the nuclear area

50
Q

chromosome condensation

A

process by which a chromosome becomes packed into a more compact structure prior to M phase of the cell cycle.

51
Q

centrosome

A

a structure present in the cytoplasm of animal cells that functions as a microtubule-organizing center and is important during cell division. a centrosome has two centrioles.

52
Q

centriole

A

structure in an animal cell that helps to organize cell division

53
Q

mitotic spindle

A

a structure made of microtubules that controls chromosome movement during mitosis

54
Q

microtubule

A

a hollow rod composed of tubulin proteins that makes up part of the cytoskeleton in all eukaryotic cells and is found in cilia and flagella. gives rigidity, shape, and organization to a cell

55
Q

kinetochore

A

a structure of proteins attached to the centromere that links each sister chromatid to the mitotic spindle.

56
Q

Metaphase plate

A

an imaginary plane during metaphase in which the centromeres of all the duplicated chromosomes are located midway between the two poles

57
Q

cell plate

A

a double membrane across the midline of a dividing plant cell, between which the new cell wall forms during cytokinesis.

58
Q

cleavage furrow

A

The area of the cell membrane that pinches in and eventually separates the dividing cell

59
Q

cleavage

A

the act or state of splitting or dividing of a cell, particularly during the telophase of (animal) cell division.

60
Q

prometaphase

A

the nuclear envelope dissolves so the chromosomes (still in their replicated form) are no longer in the nucleus, the aster has fully formed and kinetochore microtubules have attached to both sides of the centromere of each chromosome

Biology Exam 3 (6 decks)

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