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Cell & Molec FINAL > Cellular division > Flashcards

Cellular division Flashcards

1
Q

Mitosis

A

division of the nucleus

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2
Q

Cytokinesis

A

division of the cytoplasm
- creates two genetically identical daughter cells

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3
Q

Mitosis phases

A

Prophase
Metaphase
Anaphase
Telophase
- Cytokinesis

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4
Q

Chromatin

A

Chromosomes plus proteins
- RELAXED AND NON DIVIDING

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5
Q

Chromosomes

A

Contain genetic information
- CONDENSED/DIVIDING

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6
Q

Most organisms have pairs of chromosomes called what?

A

homologous chromosomes (aka homologues)
1 maternal
1 paternal

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7
Q

How many chromosomes in G1?

A

One copy of each homologous chromosome
- monad chromosome (one DNA molecule/chromosome)

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8
Q

How many chromosomes after S phase?

A

Dyad chromosomes
- two sister chromatids held together by a centromere
- TWO DNA molecules but still ONE CHROMOSOME

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9
Q

Centromere

A

constriction in the chromosome
- site of microtubule attachment during mitosis

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10
Q

DNA replication during S phase produces sister chromatids

A

One mitotic chromosome consists of TWO sister chromatids

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11
Q

Human cells

A

N= 23 chromosomes
2N= 46 chromosomes

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12
Q

After DNA replication

A

2N=46 chromosomes, so 46 times 2 chromatids per chromosome= 92 chromatids

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13
Q

What holds replicated chromosomes/sister chromatids together until mitosis?

A

Cohesin

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14
Q

Cohesin

A
  • assembled during S phase
  • forms a ring
  • by metaphase of mitosis, sister chromatids are only held together by cohesin at centromere
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15
Q

What forms the classic X-shaped metaphase chromosomes?

A

Centromeres

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16
Q

What assembles on centromeres?

A

Kinetochore

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17
Q

Kinetochore

A
  • Large complex of protein
  • Microtubules (MTs) attach here through pro-metaphase
  • MTs from each side of the cell attach to opposite sides
18
Q

What is the MicroTubule Organizing Center (MTOC) of the cell?

A

Centrosome

19
Q

Centrosome

A
  • duplicated during S phase
  • contains 2 centrioles
  • nucleate spindle microtubules
20
Q

Centrioles

A

made of two bundles of MTs arranged at right angles

21
Q

Interphase MTs are reorganized into what?

A

mitotic spindle (attach to centromeres of chromosome during pro-metaphase)

22
Q

The three types of MTs in the mitotic spindle?

A

1.) Aster
2.) Kinetochore
3.) Interpolar

23
Q

Aster spindle

A

Anchor poles to cell periphery

24
Q

Kinetochore

A

Attach to chromosomes

25
Q

Interpolar

A

Interact with MTs from opposite pole (Kinesin)

26
Q

What pushes these MTs away from each other, producing tension across spindle?

27
Q

What initiates Prophase?

A

M-cyclin/Cdk complexes

28
Q

Phosphorylation by the M-Cdk causes?

A
  • chromosome condensation
  • Mitotic spindle formation
  • Nuclear envelope breaks down releasing chromosomes into the cytoplasm
29
Q

What happens during Prophase?

A
  • chromosomes condense and become visible
  • nuclear envelope
  • nucleolus disappears
  • Centrosomes move to opposite poles (and organize the formation of the mitotic spindle apparatus made of microtubules)
30
Q

What happens during Prometaphase?

A
  • Nuclear envelope disintegrates completely
  • chromosomes begin to attach to spindle microtubules (dynamic process through which the chromosomes become attached equally to both mitotic spindles)
31
Q

What happens during Metaphase?

A
  • Sister chromatids (aka chromosomes) line up at middle of cell at the metaphase plate
  • Spindle becomes fully formed
  • Chromosomes equally attached to both mitotic spindles
32
Q

Before Anaphase . . .

A
  • Separation of the sister chromatids prevented by securin
33
Q

Securin is bound to and keeps what inactive?

34
Q

What is separase?

A

Enzyme that cleaves cohesins

35
Q

What happens during Anaphase once all chromosomes are attached to mitotic spindle?

A

Anaphase Promoting Complex (APC) is activated

36
Q

What is the Anaphase Promoting Complex?

A

a ubiquitin ligase
- APC adds ubiquitin to securin, which equals destruction

37
Q

What happens with separase is activated during Anaphase?

A
  • cuts cohesins at centromere
  • causes disjunction of sister chromatids
38
Q

What happens during Anaphase?

A

Sister chromatids separate at the centromeres
- move towards the poles

39
Q

What happens during Telophase?

A
  • Chromosomes arrive at the poles
  • Nuclear envelope reassembles
  • Chromosomes relax = indistinct chromatin again
  • Spindle disappears
  • Normal cellular function
40
Q

Late Telophase/Cytokinesis

A

process of dividing of the cytoplasm
- cells pinch off and are separated
- results in two daughter cells with identical chromosomes

Cell & Molec FINAL (8 decks)

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