Protein control of cell division

Question 1

What is the cytoskeleton?

Answer 1

A complex network of protein filaments that give mechanical support and shape to cells.

Question 2

What does the cytoskeleton consist of?

Answer 2

The cytoskeleton consists of different protein structures including microtubules which are found in all eukaryotic cells.

Question 3

What do microtubules control?

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

What involves polymerisation and depolymerisation of tubulin?

Answer 5

Formation and breakdown of microtubules involves polymerisation and depolymerisaton of tubulin.

Question 6

What forms spindle fibres that are active during cell division?

Answer 6

Microtubules form the spindle fibres that are active during cell division.

Question 7

What does the cell cycle consist of?

Answer 7

The cell cycle consists of interphase and the mitotic (M) phase.

Question 8

What does the mitotic phase involve?

Answer 8

The mitotic phase involves mitosis and cytokinesis.

Question 9

What does mitosis consist of?

Answer 9

Mitosis consists of prophase, metaphase, anaphase and telophase.

Question 10

What happens at G1?

Answer 10

Growth phase

Question 11

What happens at S?

Answer 11

Its the phase where DNA is replicated

Question 12

What happens at G2?

Answer 12

Growth phase

Question 13

What happens at Prophase?

Answer 13

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

Question 14

What happens at metaphase?

Answer 14

Chromosomes are aligned at the metaphase plate (equator of the spindle)

Question 15

What happens at anaphase?

Answer 15

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

Question 16

What happens at telophase?

Answer 16

The chromosomes decondense and nuclear membranes are formed around them.

Question 17

How is progression through the cell cycle controlled?

Answer 17

Progression through the cell cycle is controlled by checkpoints.

Question 18

What is involved in regulationg the cell cycle?

Answer 18

Cyclin proteins that accumlate during cell growth are involved in regulating the cell cycle.

Question 19

What happens at the G1 checkpoint?

Answer 19

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

Question 20

How does phosphorylation inhibit the retinoblastoma protein?

Answer 20

Phosphorylation by G1 cyclin-CDH inhibits the retinoblastoma protein (Rb)

Question 21

What happens at the G2 checkpoint?

Answer 21

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

Question 22

What does DNA damage trigger?

Answer 22

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

Question 23

What does the metaphase checkpoint control?

Answer 23

The metaphase checkpoint controls progression from metaphase to anaphase.

Question 24

What may result in degenerative diseases?

Answer 24

An uncontrolled reduction in the rate of cell cycle may result in degenerative disease.

Question 25

What may result in tumour formation?

Answer 25

An uncontrolled increase in the rate of the cell cycle may result in tumour formation.

Question 26

Is a proto-oncogene a normal gene?

Answer 26

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

Question 27

What is apoptosis triggered by?

Answer 27

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

Question 28

What do external death signals do?

Answer 28

External death signal molecules bind to a surface receptor protein and trigger a protein cascade within the cytoplasm.

Question 29

What do internal death signals result from?

Answer 29

An internal death signal results from DNA damage which causes activation of p53 tumour-suppressor protein.

Question 30

Why is apoptosis essential?

Answer 30

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

Question 31

What happens in the absense of growth factors?

Answer 31

Cells may initiate apoptosis in the absence of growth factors