Cell Division and Fate Determination

Question 1

Name the cell division stages:

Answer 1

Prophase // Prometaphase // Metaphase // Anaphase // Telophase // Cytokinesis.

Question 2

How many daughter cells are produced in mitosis?

Answer 2

2 daughter cells are produced.

Question 3

In what cell division are 4 daughter cells produced?

Answer 3

Meiosis

Question 4

Which process goes array in regards to cancer?

Answer 4

Mitosis

Question 5

Name the stages of the cell cycle:

Answer 5

G0, G1, S, G2, Mitosis and Cytokinesis.

G1, S and G2 are in the interphase stage.

Question 6

Which types of cells are part of the G0 stage?

Answer 6

If a cell can’t divide it is part of the G0 phase.
These cells are:
- Terminally differentiated.
- Senescent cells = (these are unable to grow and are permanently in G0).

Question 7

Explain briefly the cell cycle stages:

Answer 7

G1: growth and preparation of chromosomes for replication.
S: Synthesis of DNA ( and centrosomes.)
G2: Preparation of mitosis.
M: Mitotic division of cell into two daughter cells.
G0: Growth arrest (quiescence and senescence.)

Question 8

In the ‘S’ stage of the cell cycle what happens?

Answer 8

DNA replicates

Chromosomes double

Question 9

What are Okazaki fragments?

Answer 9

They are nucleotide fragments which are added in the ‘S’ phase.

Question 10

In the ‘G2 / M’ stage of the cell cycle what happens?

Answer 10

Period of rapid cell growth and protein synthesis to prepare for mitosis (M phase).

Question 11

What is p53 and why is it important?

Answer 11

p53 is a potent suppressor gene and it’s important because it prevents cancer. (known as a tumour suppressor gene.)

Question 12

What are the 3 checkpoints present in the cell cycle?

Answer 12

1) Cell growth checkpoint
2) DNA synthesis checkpoint
3) Mitosis checkpoint

Question 13

Describe the cell growth checkpoint.

Answer 13

Occurs at the end of the growth phase. Checks whether the cell is big enough and has enabled the right proteins for synthesis phase.
If not - the cell goes to the G0 phase until it is ready to divide.

Question 14

Describe the DNA synthesis checkpoint.

Answer 14

Occurs during the synthesis phase. This checks whether the DNA has been replicated correctly.
If so, the cell carries onto the mitosis phase.

Question 15

Describe the mitosis checkpoint.

Answer 15

Occurs during the mitosis phase. This checks whether mitosis is complete.
If so, the cell divides and thus, the cell repeats.

Question 16

What are cyclins?

Answer 16

They are a family of regulatory proteins which controls the progression of the cell cycle.

Question 17

How does cyclin regulate the progression of the cell cycle?

Answer 17

Cyclins regulates the cell cycle by activating CDK’s (cyclin dependant kinases) via phosphorylation. The concentration of the cyclins corresponds to the different phases of the cell cycle.

Question 18

How can you tell which stage the cell cycle is at?

Answer 18

Cyclin D: Drives the transition between G1 and S stage.
Cyclin E: Inhibits Cyclin D activity.
Cyclin A: Controls DNA copying.
Cyclin B: Drives the transition between G2 and M stage.

Question 19

Why does cyclin degradation terminate CDK activity?

Answer 19

If there is no cyclin present to bind: the CDK is not required and therefore the CDK activity ceases to exist.

Question 20

What are cyclin - dependent kinase inhibitor proteins normally used for?

Answer 20

Tumour suppressors.

Question 21

What does the G0 phase allow to happen?

Answer 21

Enables cells to undergo phenotypical changes. (IE: Become a new type of cell.)

Question 22

What key properties do stem cells have?

Answer 22

1) Potency = Can differentiate into specialist cell types.

2) Self - Renewal = Can continuously divide and replicate.

Question 23

What leads to the loss of pluripotency?

Answer 23

Specialisation of cells.

Question 24

Name the different types of stem cells:

Answer 24

Totipotent // Pluripotent // Multipotent // Unipotent

Question 25

What do the different types of stem cells do?

Answer 25

Totipotent : any cell type.
Pluripotent : Any Embryonic Stem cell type.
Multipotent: Differentiate to closely related lineages.
Unipotent: Can’t differentiate but can self renewal.

Question 26

What is quiescence?

Answer 26

The G0 phase of a cell in the cell cycle : the state of a cell when it is not dividing.

Question 27

What is senescence?

Answer 27

An irreversible form of regulated cell cycle arrest caused by multiple factors.

Question 28

Why does ageing occur?

Answer 28

Ageing is linked heavily to senescence and is due to the loss of self - renewal and cellular recovery post damage.

Question 29

What is apoptosis?

Answer 29

Apoptosis is programmed cell death which occurs in multicellular organisms.

Question 30

What occurs in apoptosis?

Answer 30

The membrane blebs (due to cytoskeleton breaking up and causing the membrane to bulge outwards) and therefore, the mitochondria disintegrates.
At this point, invagination of the cell occurs too - vesicle forms within the cells and the membrane closes around it.
The cell shrinks // chromatin condenses // DNA fragmentation.

Question 31

What happens during necrosis?

Answer 31

Traumatic cell death where there is cellular swelling. The membrane is disrupted and thus, an inflammatory response is activated.

Question 32

Describe the two major pathways in apoptosis:

Answer 32

Intrinsic: Regulated by internal stress signals. ( IE: DNA damage etc)
Extrinsic: Regulated by receptors and extracellular cues.

Question 33

How is apoptosis controlled?

Answer 33

Apoptosis is controlled via initiator caspases. These initiator caspases cleave specific proteins and thus, irreversible cell death occurs.
The amount of cleaving that the caspases do measures their activation

Question 34

What are the inhibitory regulators of apoptosis?

Answer 34

BCL2 = these regulate apoptosis.

Inhibitors of apoptosis (IAP proteins).