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BIOL 231 > Week 4_Cell division_eukaryotic cell cycle > Flashcards

Week 4_Cell division_eukaryotic cell cycle Flashcards

1
Q

what is a chromosome?

A

condensed molecules of DNA associated with proteins

a chromosome contains a particular set of genes

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2
Q

describe chromosome nomenclature:

A

you can have a 1-chromatid chromosome

you can have a 2-chromatid chromosome

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3
Q

what is a centromere?

A

an area of repetitive DNA sequence in a chromosome

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4
Q

what holds the 2 chromatids together in a 2-chromatid chromosome?

A

cohesion proteins

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5
Q

during cell division, ___ attach to the centromere of each sister chromatid

A

2 types of proteins
- cohesion proteins
- kinetochore proteins

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6
Q

what are cohesion proteins?

A

holds the sister chromatids together after DNA replication (inner part of the centrosomes)

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7
Q

what are kinetochore proteins?

A

outer part of the centromeres

the site of microtubule attachment during cell division

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8
Q

what are telomeres?

A

repetitive sequences of DNA that protect and stabilize the ends of chromosomes

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9
Q

each time a cell divides, the telomeres become ___

A

shorter

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10
Q

each time a cell ___, the telomeres become shorter

A

divides

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11
Q

once the telomeres become too short, the cell…

A

can no longer divide

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12
Q

telomere length can be maintained by the enzyme ___

A

telomerase

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13
Q

most cells in the body stop producing telomerase after ___

A

embryonic development

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14
Q

in ~90% of human cancers, telomerase production has been ___

A

reactivated

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15
Q

each human cell contains ~___ of DNA

A

2 meters

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16
Q

the nucleus of a human cell, which contains the DNA, is only ~___ in diameter

A

6 micrometers

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17
Q

how does DNA coil?

A

DNA has a (-) charge
histone proteins have a (+) charge

146 bp of DNA wraps around 8 histone proteins to form a nucleosome

nucleosomes coil into a selenoid

selenoids are compacted further into supercoils

the level of DNA compaction changes (it’s dynamic)

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18
Q

what is chromatin?

A

chromosomal DNA associated with proteins

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19
Q

what is a nucleosome?

A

the basic unit of chromatin

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20
Q

how is a nucleosome made?

A

146 bp of DNA wrapped around 8 histone protiens

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21
Q

describe the DNA compaction levels

A

DNA wraps around histone proteins to form nucleosomes

nucleosomes coil into selenoids

selenoids compact further into supercoils

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22
Q

during lower level of DNA compaction, individual chromosomes ___ distinguishable

A

are not

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23
Q

during higher level of DNA compaction, individual chromosomes ___ distinguishable

A

are

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24
Q

cell division in eukaryotes is under strict genetic control in a process called the ___

A

cell cycle

25
Q

list the 5 main phases of the cell cycle:

A

G1

S

G2

M

cytokinesis

26
Q

describe G1:

A

1st phase of cell cycle

first gap phase (pre-DNA replication

carry out metabolic activity and preparing for DNA replication

27
Q

describe S:

A

2nd phase of cell cycle

DNA synthesis == DNA replication

28
Q

describe G2:

A

3rd phase of cell cycle

2nd gap phase (post-DNA replication)

metabolize and prepare for DNA segregation

29
Q

describe M:

A

4th phase of cell cycle

mitosis (or meiosis)

DNA is segregated

30
Q

describe cytokinesis

A

5th phase of cell cycle

division of cytoplasm into 2 cells

31
Q

what is Interphase?

what phases make up interphase?

A

G1, S, G2

the metabolically active period b/n nuclear divisions

32
Q

mitosis + cytokinesis is…

A

sometimes collectively called “mitosis” but they are separate events

33
Q

the cell cycle is an oscillation b/n ___, ___, and ___

A

interphase, mitosis, and cytokinesis

34
Q

what is G0?

A

the cell is in a non-dividing state

35
Q

the cell cycle is controlled in part by a class of proteins called ___

A

cyclins

36
Q

what are cyclins?

A

regulatory proteins that accumulate and degrade in a cell-cycle specific fashion

37
Q

without cyclin proteins, the cell cycle would ___

A

stop

38
Q

cyclins regulate….

A

kinases and CDKs

39
Q

what are kinases?

A

protein enzymes that phosphorylate (add a phosphate group to) other molecules

40
Q

what are phosphatases?

A

enzymes that dephosphorylate (remove a phosphate group from) other molecules

41
Q

how does an enzyme get activated?

A

getting phosphorylated

42
Q

cyclins regulate ___ (CDKs)

A

cyclin dependent kinases

43
Q

what are CDKs and how are they activated?

A

kinases that are inactive unless they are attached to a cyclin protein

44
Q

when activated by a cyclin, CDKs can…

A

phosphorylate and activate target proteins that are necessary to advance the cell cycle

45
Q

the activation of CDKs by cyclins ultimately results in…

A

the activation of specific genes that are necessary to advance the cell cycle

46
Q

describes steps and progression of the cell cycle

A

1) cyclins are produced

2) inactive CDKs

3) active cyclin/CDK complex

4) CDK phosphorylates/activates target proteins

5) activated target proteins advance the cell cycle

47
Q

cyclins are needed to proceed through ___

A

cell cycle checkpoints

48
Q

what are cell cycle checkpoints?

A

points during the cell cycle at which the progression of the cell cycle can be stopped

49
Q

what is the purpose of having cell cycle checkpoints?

A

defense against:

  • improper environmental conditions
  • incompletely replicated or damaged DNA
  • misaligned chromosomes
50
Q

what are the 3 main cell cycle check points?

A

1) G1/S transition (start or restriction checkpoint)

2) G2/M transition checkpoint

3) Spindle checkpoint

51
Q

describe the G1/S transition checkpoint

A

start or restriction checkpoint

the commitment to divide at all

regulated by cyclin/CDKs

52
Q

describe the G2/M transition checkpoint

A

the commitment to proceed into mitosis

regulated by cyclin/CDKs

53
Q

describe the Spindle checkpoint

A

commitment to segregate the replicated DNA to opposite ends of the cell (anaphase)

regulated by APC (anaphase promoting complex)

APC is not a cyclin/CDK complex

54
Q

what happens if the cell fails the test at any checkpoint?

A

cell division is halted for repairs or cell death is induced (apoptosis)

55
Q

what do the cyclin/CDKs check for in G1/S checkpoint?

A

proper environmental conditions

sufficient nutritional state of cell

sufficient size of cell

56
Q

what do cyclin/CDKs check for in G2/M checkpoint?

A

is DNA completely replicated

no DNA damage

sufficient size of cell

57
Q

what do APCs check for in “spindle” checkpoint?

A

are the chromosomes aligned properly for DNA segregation

58
Q

genes that control ___ are the most frequently mutated genes in all forms of cancer

A

the cell cycle

59
Q

describe how cancer cells continue to accumulate mutations and become more and more difficult to treat

A

cells start the cell cycle when they shouldn’t

cells proceed to mitosis/cytokinesis when they shouldn’t

cells don’t die when they should (evasion of apoptosis)

BIOL 231 (23 decks)

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