Cell Cycle

Question 1

Interphase

Answer 1

G1 – growth phase
S phase - DNA is replicated
G2 - further growth phase

Question 2

Mitotic Phase (M) (Mitosis – PMAT C)

Answer 2

Chromosomal material is separated by the spindle microtubules. Cytokinesis takes place in which the cytoplasm is separated into two daughter cells

• Prophase
• Metaphase
• Anaphase
• Telophase

Question 3

Prophase

Answer 3

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 4

Metaphase

Answer 4

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

Question 5

Anaphase

Answer 5

as spindle microtubules shorten by depolymerisation (contract), sister chromatids are separated, and the chromosomes are pulled to opposite poles.

Question 6

Telophase

Answer 6

Chromosomes decondense and nuclear membranes are formed around them

Question 7

Key check points of Cell cycle

Answer 7

G1 checkpoint
G2 checkpoint
Metaphase checkpoint

Question 8

G1 checkpoint

Answer 8

• Rb acts as a tumour suppressor by inhibiting the transcription of genes that code for proteins needed for DNA replication.
• Phosphorylation by G1 cyclin-CDK inhibits the Rb. This allows transcription of the genes that code for proteins needed for DNA replication. Cells progress from G1 to S phase.

Question 9

G2 checkpoint

Answer 9

• Success of DNA replication & any damage to DNA is assessed.
• DNA damage triggers the activation of several proteins including p53 that can stimulate DNA repair, arrest the cell cycle or cause cell death

Question 10

Metaphase checkpoint

Answer 10

Progression is halted until the chromosomes are aligned correctly on the metaphase plate and attached to the spindle microtubules.

Question 11

Cyclins

Answer 11

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

Question 12

How can changes in cell cycle cause degenerative disease

Answer 12

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

Question 13

How can tumour be formed? (cell cycle)

Answer 13

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

Question 14

what is Apoptosis?

Types?

Answer 14

activation of caspases (types of protease enzyme) that cause the destruction of the cell. Due to;

• External death signal
• Internal

Question 15

Importance Of apoptosis

Answer 15

Essential during development of an organism to remove cells no longer required as development progresses or during metamorphosis
Cells may initiate apoptosis in the absence of growth factors

Question 16

External death signal

Answer 16

• From lymphocytes

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

Question 17

Internal Death Signal

Answer 17

• From DNA damage

- Causes activation of p53 tumour suppressor protein