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BIO112 > Unit 2 Chapter 11: The Cell Cycle + Mitosis > Flashcards

Unit 2 Chapter 11: The Cell Cycle + Mitosis Flashcards

1
Q

What are the 3 mysteries of heredity

A
  1. all organisms come from other organisms
  2. children resemble their parents
  3. siblings are not identical
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2
Q

What is the cell theory (3 points)

A
  1. all organisms consist of cells
  2. cells divide to produce new cells
  3. higher organisms fuse their cells to produce a new organism
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3
Q

What are mitosis and cytokinesis responsible for (3 events)

A
  1. growth
  2. wound repair
  3. reproduction
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4
Q

What is asexual reproduction

A

produces offspring that are genetically identical from the parent, ie. mitosis

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5
Q

What is a chromosome

A
  • a single string of DNA
  • linear in eukaryotes
  • circular in bacteria
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6
Q

What does DNA do

A

stores the cell’s heredity info or genetic material

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7
Q

What is a gene

A

a length of DNA that codes for a particular protein or RNA found in the cell

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8
Q

Why can we see chromosomes

A

they condense by associating with histones (proteins) and forming chromatin

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9
Q

What is a chromatid

A

one of the DNA copies in a replicated chromosome

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10
Q

What is a centromere

A

the specialized region that joins 2 chromatids togethe

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11
Q

What are sister chromatids

A

chromatids from the same chromosome

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12
Q

What is a karyotype

A

a way of organizing and identifying chromosomes

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13
Q

What are homologs

A

nearly identical pairs of chromosomes

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14
Q

What are mitotic chromosomes

A

2 chromosomes bound by a centromere (technically thats 2 pieces of DNA but we still call them chromosomes)

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15
Q

What does “segregating is exacting mean”

A
  • organisms need at least 1 of each chromosome because each has specific genetic material
  • usually we need EXACTLY one of each
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16
Q

What is the cause of down syndrome

A

3 chromosome 21

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17
Q

What is interphase

A

DNA is found in nucleus associated with histones (as chromatin)

  • active time: cell is either growing and preparing to divide or performing its specialized function
  • includes S phase
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18
Q

What is S-phase

A
  • in interphase

- DNA is replicated

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19
Q

What is G2

A

the time lag that occurs after S phase and before M phase

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20
Q

What is G1

A

the time lag that occurs after M phase and before S phase (longer than G2)

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21
Q

Why are G2 and G1 necessary

A

the cells need to grow and synthesize enough organelles so its daughter cells will be normal in size and function

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22
Q

What is mitosis

A

the process where cells divide to make identical copies of themselves and each daughter cell inherits one copy of each chromosome

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23
Q

What do cohesins do

A

protein rings made of 3 subunits that encircle 2 pieces of DNA to keep them together until they receive the division signal

24
Q

What do condesins do

A

protein rings made of 3 subunits that encircle DNA and stabilize loops in the same piece of DNA (to make them smaller/more condensed)

25
Q

What are the steps of mitosis

A

IPPMAT

  • interphase
  • prophase
  • prometaphase
  • metaphase
  • anaphase
  • telophase/cytokinesis
26
Q

What happens in prophase

A

-chromosomes condense
-spindle apparatus forms
(centrosomes move to poles)

27
Q

What is the spindle apparatus

A
  • consists of microtubules (polar and kinetochore)

- produces forces that pull chromosomes to poles and push cell poles away from eachother

28
Q

What are polar microtubules

A

extend from each spindle (centrosome which contains centrioles) and overlap each other in middle of cell

29
Q

What are kinetochore microtubules

A

attach to chromosomes (kinetochore, at centromere region)

-each chromosome has 2 kinetochores

30
Q

What happens in prometaphase

A
  • nuclear envelope disappears
  • kinetochore microtubules attach to one of the 2 sister chromatids of each chromosome at the kinetochore
  • centrosomes continue moving to poles, kinetochore microtubules start moving chromosomes to center
31
Q

What happens in metaphase

A
  • cells line up in centre (metaphase plate)

- polar microtubules create this pole to pole connection by overlapping

32
Q

What happens in anaphase

A
  • cohesins split
  • sister chromatids are pulled apart to opposite poles (replicated chromosomes separate into 2 identical sets of unreplicated chromosomes)
33
Q

What happens in telophase/cytokinesis

A
  • nuclear envelope reforms
  • spindle apparatus disappears
  • chromosomes decondense
  • 2 nuclei form
  • cell pinches off and divides (cleavage furrow) (actin and myosin)
34
Q

What is cytokinesis like in plants

A

vesicles from golgi line up and from a cell plate which builds up and divides the 2 cells

35
Q

Which ends of the microtubule attach to the kinetochore

A

plus end

36
Q

How do chromosomes move during mitosis

A
  • the kinetochore microtubules shorten because tubulin subunits are lost from plus ends
  • as anaphase occurs, proteins in kinetochore catalyze the loss of tubulin subunits at plus ends of the tubules, while proteins walk towards minus end
  • this pulls chromosomes to opposite sides of the cell
37
Q

What type of cells does mitosis produce

A

diploid

38
Q

How is the cell cycle regulated

A

various cyclins which are the second MPF (mitosis promoting factor)subunit

  • cyclin concentrations fluctuate throughout the cell
  • protein kinase subunit of MPF is cyclin-dependent kinase
  • cyclin functions as regulatory protein and kinase catalyzes the phosphorylation of other proteins to start mitosis
39
Q

How is MPF activated

A

when one of the phosphate groups on the Cdk subunit drops off in G2 and causes shape to change

40
Q

How is MPF deactivated

A

during anaphase, enzymes degrade MPF’s cyclin subunit which leads to its own destruction

41
Q

What is the G1 checkpoint

A

-between G1 and S phase
-establishes whether cell will continue through cycle and divide or go to G0
factors:
-size-cells are arrested if too small
-availability of nutrients-arrested if nutrient conditions are poor
-social signals
-damage to DNA

-if damaged DNA is not stopped, can lead to uncontrolled cell division, cells will enter cell cycle without growing getting smaller each time

42
Q

What is the G2 checkpoint

A

-after S phase and between G2 and M phase
-if DNA is damaged or not replicated correctly, cells can’t pass
-size could also be a factor
-

43
Q

What is the S to G2 checkpoint

A
  • ensures cells are replicated
  • hydroxyurea blocks chromosome replication so cells stay in S phase
  • caffeine disables this checkpoint
44
Q

What happens when both hydroxyurea and caffeine are added

A

DNA cannot replicate, still enters mitosis and then everything dies

45
Q

What is the metaphase checkpoint

A
  • if not all chromosomes attach to spindle properly, mitosis stops at metaphase
  • anaphase delayed until everything attaches properly
46
Q

What is cancer and how does it arise

A
  • the uncontrolled division of cells

- arise from cells in which cell checkpoints have failed

47
Q

What are the 2 defects of cancerous cells

A
  1. defects that make proteins required for cell growth active when they shouldn’t be
  2. defects that prevent tumor suppressing genes from shutting down the cell cycle
48
Q

How do cells become malignant and cancerous

A

if they can detach from the original tumour and invade other tissues

49
Q

What is the G0 phase

A

-where mature cells go, when their cell cycle is arrested in G1

50
Q

Which check point is most crucial when it comes to cancer

A

G1 because it looks for external signals which can be manipulated

51
Q

What is cancer characterized by

A
  1. loss of control at G1 checkpoint which leads to crazy cell division
  2. metastasis
52
Q

Progression through the cell cycle is regulated by oscillations in the concentration of

A

cyclins

53
Q

What signals a cell to divide

A

the binding of Cyclin D (only in G1) and Cdk4 (always in cell)

54
Q

Which cells don’t bother with cytokinesis

A

muscle cells

55
Q

How many chromosomes do humans have

A

46, 23 pairs

BIO112 (19 decks)

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