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Foundations Part II > Mitosis and Meiosis > Flashcards

Mitosis and Meiosis Flashcards

1
Q

Stages of mitosis

A
  1. Early Prophase
  2. Late Prophase
  3. ProMetaphase
  4. Metaphase
  5. Early Anaphase
  6. Anaphase
  7. Telophase

Know how these stages look like under Light microscope

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2
Q

Early Prophase

A
  1. Early Prophase: replicated chromosomes condense
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3
Q

Late Prophase

A
  1. Late Prophase: microtubules have self assembled. Centromeres that have replicated move apart
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4
Q

Prometaphase

A
  1. ProMetaphase: This marks the beginning of the break down of the nuclear envelope. This allows the spindles and the microtubules to interact with the recently condensed chromosomes
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5
Q

Metaphase

A
  1. Metaphase: chromosomes are aligned along the equator forming the metaphase plate (and bipolar spindle is clear - not sure what this means)
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6
Q

Early Anaphase

A
  1. Early Anaphase: cohesions degrade, sister chromatids separate resulting in daughter chromosomes moving to 2 opposite pole
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7
Q

Anaphase

A
  1. Spindle moves further apart enhancing the separation of chromosomes
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8
Q

Telophase

A
  1. Telophase: daughter nuclei go apart
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9
Q

What are the characteristics of tubulin growth

A

Combines with GTP, actively polymerizes, if not bound to GTP depolymerizes and kinks

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10
Q

What are the subunits that make tubulin

A

Alpha and beta tubulin make the long fiber, gamma tubulin is at the centrosome and stabilizes tubulin at the negative end

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11
Q

What are the features of the process of tubulin polymerization

A

The process is very dynamic, there are proteins that either stabilize or destabilize tubulin

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12
Q

What are centrosomes

A

Microtubule organizing centers

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13
Q

What does tubules from the centrosomes do

A

They reach out to a part of the chromosome called the centromere and they will bind to it. Several proteins are involved in this process and together with microtubules they form a kinetochore complex. This complex stabilizes the plus end of the microtubules

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14
Q

What are the fibers called in kinetochore

A

K fibers or kinetochore fibers

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15
Q

What other fibers are involved in this process

A

There are fibers called astral fibers that do not find a centromere and they keep growing and lock on to the cell’s cortex. This anchors these microtubules and allows leverage to put a force on the chromsomes in the process of pulling them apart

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16
Q

Name the 3rd fibers involved here in metaphase

A

These fibers are called Overlapping mt that grow past the equator and bind with kinesins which are the motors so they are the ones that apply the force

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17
Q

What are gamma tubulesin turn stabilized by

A

Mt associated proteins stabilize gamma tubules

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18
Q

What is the cloud space around the centrosomes

A

Pericentriolar space that have proteins that helps in the oraganization of the centrosomes and the microtubules

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19
Q

When does the mother centrosome replicate

A

During interphase

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20
Q

What is the function of centrosome in a terminally differentiated cell

A

It makes cilia

21
Q

How does the centrosome replicate

A

During S phase CDK2 is activated that p’s alot of stuff, causes the mother centrosome to break apart and replicate

22
Q

What is the function of pericentriolar proteins

A

It tightly regulates the centrosome function

23
Q

How are these proteins regulated

A

By p’s, protein expression and protein interaction

24
Q

What causes abnormal centrosome replication and what is the result

A

Alterations in the interacts or in the structure of pericentriolar proteins themselves can lead to abnormal centrosome replication.

Result is that it impairs mitosis.

25
Q

What are the steps when a cell has abnormal centrosome replication

A

There is a centrosome checkpoint that we will later talk about. The cell makes alot of p53 which shuts down cell cycle. If the damage is too great it can lead to cell apoptosis

26
Q

What happens if the p53 itself is messed up

A

The cell cycle wont be shut down, the cell will continue with mitosis with abnormal centrosomes and this leads to aneuploidy. Almost all solid cancers have aneuploidy.

27
Q

What lies on the centromere

A

The kinetochore

28
Q

What are its 2 functions

A

It stabilizes the + end of the tubulin and binds to a specific region of the DNA called the centromere

29
Q

What is a centromere

A

It is part of the DNA that is in the center. here the histones are different such that it has nucleosomes that the kinetochore protein can latch on to. These histones are called CENPA.

Also in this region you can find the cohesion

30
Q

What are the 3 kinases that are important in the formation of mitotic spindle

A

They are Aurora Kinases A and B and Polo Like Kinases

31
Q

What are their functions

A

Aurora A: Localized at the centrosome
Aurora B: localized to the kinetochore/spindle midzone
Polo like kinase is at both the centrosome and the kinetochore

32
Q

When are these kinases found

A

Only during the M phase

33
Q

How many kinetochores are there on chromosomes

A

There are 2 kinetochores on either side of a chromosome that is supposed to be split into 2 daughter chromosomes

34
Q

What is MCC

A

Mitotic Checkpoint Complex. When only one of the kinetochore is bound to the kinetochore proteins and starts pulling the chromosome on one side, the unattached kinetochore forms the MCC so it destabilzies the other kinetochore to stop pulling of the chromsome

35
Q

What is an Anaphase Promoting Complex

A

It is Ubiquitin Ligase (E3). It has many factors and proteins associated with it. This proteins can be interchanged to form different forms of APC. These proteins will form APC at different times and at different cell cycles

36
Q

What is the function of APC

A

It forms most of the spindle assembly checkpoint

37
Q

How does kinetochore send a wait signal

A

When they are not bound to mt on one side they send out a ‘WAIT’ signal which are the MAD1 and MAD2 proteins.

MAD2 complex binds with APC and also brings with it BUBR1 and BUB3 which are a part of the MCC. This inhibits APC.

38
Q

What happens to MAD2 in unattached kinetochore

A

MAD2 goes on and finds CDC20. It binds to the complex of APC-CDC20 and recruits BUBR1 and BUB3. This causes the APC to become inactive so it cannot degrade securin (which has to be removed to break down the cohesion complex) and cyclin B. So the cell now cannot proceed to Anaphase

39
Q

What happens to MAD2 when all the kinetochores are attached

A

MAD2 in its open from interacts with dynin which is a motor protein and is taken all the way to centrosome so it does not inhibit APC anymore. Now even if APC is inactive due to binding of CDC20 and BUBR1 and BUB3, this complex will soon degrade making the APC active again and now the cell can go on and proceed to anaphase

40
Q

What is broken down when the cell enters prometaphase and who causes the breakdown of this compound

A

Cyclin A, APC

41
Q

What is broken down when the chromosomes align themselves at the equator, what breaks it down

A

Cyclin B, APC

42
Q

How are the DNA pulled apart

A

By motor proteins called kinesins and the dyenins that bind to mt and pull the DNA apart

43
Q

How is cytokinesis carried out

A

Formation of actin ring at the midbody that pinch the cell until it falls apart

44
Q

What is Taxol, what does it do?

A

It is an anticancer drug. It binds to tubulin and stabilizes it. So the cell cant seperate its DNA

45
Q

What is SAC

A

MAD2 and CDC20

46
Q

When does SAC come in to play

A

When the kinetochore is attached to only 1 side, SAC comes in and recruits MCC which is BUBR1 and BUB3. This binds with the APC and bind it to stop it from functioning

47
Q

What kind of DNA is in the centromere

A

Satellite DNA

48
Q

What contracts the actin ring to pinch off the cytoplasm

A

Aurora B and PLK

Foundations Part II (31 decks)

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