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 depolymerisation 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

It’s 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 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 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 regulating the cell cycle

Answer 18

Cyclin proteins that accumulate 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 transcription 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-CDK 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 the 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 the development of an organism to remove cells no longer required as development progresses or during metamorphosis.

Question 31

What happens in the absence of growth factors

Answer 31

Cells may initiate apoptosis in the absence of growth factors.