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Cell Bio > Lecture 7 > Flashcards

Lecture 7 Flashcards

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Biology 101 flashcards
1
Q

During _____, centrosomes begin to move apart and migrate to the poles for the orientation of the
mitotic apparatus

A

prophase

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2
Q

_____ motor protein (walks towards the minus end) pulls the astral
microtubules to the cell cortex, during prophase

A

Dynein

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3
Q

_____ motor protein (walks
towards the plus end) cross-links non-kinetochore microtubules and pushes
the centrosomes apart, in prophase

A

Kinesin

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4
Q

Microtubules begin making contact with
chromosomes in _______ when the
nuclear envelope breaks down

A

prometaphase

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5
Q

true/false: microtubules are constantly extending from and drawing
back to the centrosome

A

true

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6
Q

true/false: microtubules don’t have initial unstable attachments

A

false

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7
Q

Eventually, the chromosomes become equidistant from the
poles – forming the _______

A

metaphase plate

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8
Q

The sister chromatins are held together by
protein complexes called
_______

A

cohesins

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9
Q

Cohesin linkage of chromatids is broken by the
enzyme ______

A

separase

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10
Q

Anaphase begins when the
inhibitor of separase, _______, is tagged and degraded by APC/C

A

securin

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11
Q

_______ triggers sister-chromatid separation at anaphase

A

Proteolysis

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12
Q

________: poleward
movement of the chromosomes
accompanied by shortening of
the kinetochore microtubules.

________: The separation of
the spindle poles themselves

A

Anaphase A
Anaphase B

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13
Q

What happens when all chromosomes are not properly attached?

A

polyploidy- some progeny have less or more chromosomes

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14
Q

The kinetochores of unattached chromosomes send a “stop” signal
to the cell-cycle control system at the ___________, this signal results in the blocking of the activation of APC/C, and as
a result, chromosomes remain glued together

A

Spindle assembly checkpoint

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15
Q

what are the two consequences of blocking APC/C?

A

It blocks the destruction of cyclins by APC/C

Cdks remain active— delays mitosis

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16
Q

how do we re-form the nuclear envelope in telophase?

A

Dephosphorylation of nuclear pore proteins and lamins at
telophase helps reverse the process

  • the phosphorylation of these proteins DISASSEMBLE the nuclear envelope in prometaphase, so the de-phosphorylation reverses this!
17
Q

true/false: Mitosis is complete with the formation
of nuclear envelope

A

true

18
Q

when is the first visible sign of cytokinesis?

A

anaphase

19
Q

__________: Requires the formation of a structure based on actin and myosin filaments (the contractile ring)

A

cytokinesis

20
Q

Where is the plane of cleavage going to be? in cytokinesis

A

Perpendicular to the long axis of the mitotic
spindle, not neccesarily in the middle!

21
Q

how does cytokinesis happen in plants?

A

cell walls! New cell wall starts to assemble inside the cell at the equator of the old spindle after the chromosome segregation- fuses to form new cell wall

22
Q

what is the first level of DNA packing?

A

histones

23
Q

what are nucleosomes made of?

A

DNA sequence wrapped around a core of
histone proteins

24
Q

How is DNA held to histones?

A

DNA is held by the histones due to non-covalent bonds, especially ionic bonds between negatively charged phosphate
backbone of DNA and positive charge
of histones

25
Q

what are the four types of histones in the nucleosome core? how many are there?

A

Two of each: Histones H2A, H2B, H3 and H4

26
Q

what is the fifth type of histone? what is it used for?

A

Histone H1 (fifth type) –the linker histone, links adjacent nucleosome core particles

27
Q

true/false: there is a total of 168 nucleotide bases per unit
7:1 packing ratio, the fiber is 10nm thick

A

true

28
Q

true/false: DNA wraps around the nucleosomes 1.8 turns or 146 nucleotide bases per
nucleosome

A

true

Cell Bio (11 decks)

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