Protein control of cell division

Question 1

what is the function 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

what are micro-tubules

Answer 3

Microtubules are hollow cylinders composed
of the protein tubulin. They radiate from the
microtubule organising centre (MTOC) or
centrosome.

Question 4

what do the microtubules controls

Answer 4

Microtubules control the movement of
membrane-bound organelles and
chromosomes

Question 5

what does cell division require

Answer 5

Cell division requires remodelling of the
cytoskeleton

Question 6

what does the Formation and breakdown of microtubules
involve

Answer 6

Formation and breakdown of microtubules
involves polymerisation and depolymerisation
of tubulin

Question 7

what do micro tubules form

Answer 7

Microtubules form the spindle fibres that are
active during cell division

Question 8

what does the cell cycle consist of

Answer 8

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

Question 9

what does the mitoic phase invovle

Answer 9

Mitotic phase involves mitosis and
cytokinesis

Question 10

what does inter phase involve

Answer 10

Interphase involves growth and DNA
synthesis including G1, a growth phase; S
phase, during which the DNA is replicated;
and G2, a further growth phase.

Question 11

In mitosis what is the chromosomal material separated by

Answer 11

In mitosis the chromosomal material is separated by the spindle microtubules. This
is followed by cytokinesis, in which thecytoplasm is separated into two daughter
cells.

Question 12

what does mitosis consist of

Answer 12

Mitosis consists of prophase, metaphase,
anaphase and telophase

Question 13

what happens in prophase

Answer 13

Prophase — 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 during metaphase

Answer 14

Metaphase — chromosomes are aligned at
the metaphase plate (equator of the spindle).

Question 15

what happens during anaphase

Answer 15

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

Question 16

what happens during telophase

Answer 16

Telophase — the chromosomes decondense
and nuclear membranes are formed around
them.

Question 17

what is progression through the cell cycle controlled by

Answer 17

Progression through the cell cycle is controlled by checkpoints

Question 18

what are checkpoints

Answer 18

Checkpoints are mechanisms within the cell
that assess the condition of the cell during
the cell cycle and halt progression to the next
phase until certain requirements are met.

Question 19

what are cyclin proteins that accumulate during cell growth involved in

Answer 19

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

Question 20

Cyclins combine with and activate cyclindependent kinases (CDKs). Active cyclinCDK complexes do what

Answer 20

Cyclins combine with and activate cyclindependent kinases (CDKs). Active cyclinCDK complexes phosphorylate proteins that
regulate progression through the cycle. If sufficient phosphorylation is reached, progression occurs.

Question 21

what happens at the G1 checkpoint

Answer 21

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 22

wshat does phosporylation by G1 cylclin-CDK inhibit

Answer 22

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

Question 23

what happens at the G2 checkpoint

Answer 23

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

Question 24

what does

Answer 24

This allows transcription of the genes that code for proteins needed for DNA replication. Cells progress from G1 to S phase

Question 25

DNA damage triggers the activation of several proteins including what

Answer 25

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

Question 26

what doe a metaphase checkpoint control

Answer 26

A metaphase checkpoint controls progression from metaphase to anaphase

Question 27

at the metaphase checkpoint what happens

Answer 27

At the metaphase checkpoint, progression is
halted until the chromosomes are aligned
correctly on the metaphase plate and attached to the spindle microtubules.

Question 28

An uncontrolled reduction in the rate of the cell cycle may result in what?

Answer 28

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

Question 29

An uncontrolled increase in the rate of the cell cycle may result in what?

Answer 29

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

Question 30

What is a proto-oncogene

Answer 30

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

Question 31

what is apoptosis triggered by

Answer 31

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

Question 32

The production of death signal molecules from lymphocytes is an example of what

Answer 32

The production of death signal molecules from lymphocytes is an example of an external death signal. DNA damage is an
example of an internal death signal.

Question 33

External death signal molecules bind to a
surface receptor protein and trigger what

Answer 33

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

Question 34

what does an internal death signal resulting from DNA damage cause

Answer 34

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

Question 35

What do both types of death signal result in what?

Answer 35

Both types of death signal result in the activation of caspases (types of protease
enzyme) that cause the destruction of the cell

Question 36

apoptosis is essential during what?

Answer 36

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

Question 37

cells may initiate apoptosis in absence of what?

Answer 37

Cells may initiate apoptosis in the absence of growth factors