Protein control of cell division

Question 1

Function of the cytoskeleton

Answer 1

The cytoskeleton gives mechanical support and shape to cells

Question 2

What does the cytoskeleton consist of?

Answer 2

It consists of different protein structures including microtubules, which are found in all eukaryotic cells

Question 3

Function of microtubule

Answer 3

Microtubules control the movement of membrane-bound organelles and chromosomes

Question 4

What does cell division require?

Answer 4

Cell division requires remodelling of the cytoskeleton

Question 5

Formation and breakdown of microtubules involves?

Answer 5

polymerisation and depolymerisation of tubulin

Question 6

Microtubule can form?

Answer 6

spindle fibres that are active during cell division

Question 7

The cell cycle consists of?

Answer 7

interphase and mitotic (M) phase

Question 8

Mitotic phase consists of?

Answer 8

mitosis and cytokinesis

Question 9

Mitosis consist of?

Answer 9

prophase, metaphase, anaphase and telophase

Question 10

How to control progression of cell cycle?

Answer 10

checkpoints

Question 11

What are cyclins?

Answer 11

Cyclins are proteins that accumulate during cell growth are involved in regulating the cell cycle

Question 12

What happens at G1 checkpoint?

Answer 12

At the G1 checkpoint, retinoblastoma protein (Rb) acts as a tumour suppressor by inhibiting the transcription of genes that code for proteins needed for DNA replication

Question 13

What is the goal of mitosis?

Answer 13

To make identical cells

Question 14

How to inhibit retinoblastoma proteins? Why?

Answer 14

Phosphorylation by G1 cyclin-CDK. This means that it can no longer bind the transcription factor. This allows transcription of the genes that code for proteins needed for DNA replication and allows cells to progress from G1 to S phase.

Question 15

What does non-phosphorylated form of Rb do?

Answer 15

restricts progression from G1 phase into S phase by binding to a transcription factor, therefore preventing transcription of certain genes required for S phase to begin; thus the cell remains in G1

Question 16

What is the G2 checkpoint?

Answer 16

At the G2 checkpoint, the success of DNA replication and any damage to DNA is assessed

Question 17

What happens if there is DNA damage?

Answer 17

DNA damage triggers the activation of several proteins including p53 that can stimulate DNA repair, arrest the cell cycle or cause cell death

Question 18

What happens at metaphase checkpoint?

Answer 18

A metaphase checkpoint controls progression from metaphase to anaphase

Question 19

What can cause a degenerative disease?

Answer 19

An uncontrolled reduction in the rate of the cell cycle

Question 20

What can cause tumour formation?

Answer 20

An uncontrolled increase in the rate of the cell cycle

Question 21

What is a proto-oncongene?

Answer 21

It is a normal gene, usually involved in the control of cell growth or division, which can mutate to form a tumour-promoting oncogene

Question 22

Apoptosis is triggered by what?

Answer 22

is triggered by cell death signals that can be external or internal

Question 23

What is an external death signal molecule?

Answer 23

bind to a surface receptor protein and trigger a protein
cascade within the cytoplasm

Question 24

What is an internal death signal molecule? What causes it?

Answer 24

An internal death signal resulting from DNA damage causes activation of p53 tumour suppressor protein

Question 25

What do both types of death signals activate?

Answer 25

Both types of death signal result in the activation of caspases that cause the destruction of the cell

Question 26

What are caspases

Answer 26

types of protease enzyme

Question 27

Why is apoptosis essential?

Answer 27

Apoptosis is essential during development of an organism to remove cells no longer required as development progresses or during metamorphosis

Question 28

Why might cells initiate apoptosis?

Answer 28

Cells may initiate apoptosis in the absence of growth factors

Question 29

Prophase?

Answer 29

DNA condenses into chromosomes each consisting of two sister chromatids.
Nuclear membrane breaks down; spindle microtubules extend from the MTOC by polymerisation and attach to chromosomes via their kinetochores in the centromere region.

Question 30

Metaphase?

Answer 30

Chromosomes are aligned at the metaphase plate (the term metaphase plate is used to describe the arrangement of the chromosomes at the equator of the cell)

Question 31

Anaphase?

Answer 31

As spindle microtubules shorten by depolymerisation, sister chromatids are separated, and the chromosomes are pulled to opposite poles

Question 32

Telophase

Answer 32

The chromosomes decondense and nuclear membranes are formed around them.
Cytokinesis also takes place during this period, which involves the separation of the cytoplasm into two daughter cells

Question 33

Interphase sub phases?

Answer 33

G1, S and G2

Question 34

G1 phase?

Answer 34

G1 is the first ‘growth’ phase; it is a growth period where proteins and organelles are synthesised.

Question 35

S phase?

Answer 35

DNA is replicated in preparation for mitosis

Question 36

G2 phase?

Answer 36

this is another growth period during which proteins and organelles are synthesised