6. Cell cycle, mitosis, meiosis and recombination

Question 1

What are the main stages of interphase?

Answer 1

G1 - growth phase, cell contents excluding chromosomes are duplicated, no DNA synthesis

S - DNA replicated. 1 chromosome = 2 sister chromatids

G2 - growth phase, duplicated chromosomes checked for errors

Question 2

What are the main stages of mitosis?

Answer 2

Prophase - chromosomes condense, spindle fibres appear, nuclear membrane breaks down

Prometaphase - spindle fibres attach to chromosomes

Metaphase - chromosomes align at metaphase palte

Anaphase - centromeres divide, sister chromatid move to opposite poles

Telophase - nuclear membrane reforms, chromosomes condense, spindle fibres disappear

Cytokinesis - cytoplasm divides

Question 3

What is the first checkpoint in the cell cycle?

Answer 3

G1/S restriction checkpoint - checks cell is large enough to divide, has sufficient energy reserves and is receiving appropriate molecular signals (growth factors)

Question 4

What is the second checkpoint in the cell cycle?

Answer 4

G2/M checkpoint - checks DNA was completely copied and none is damaged.

If DNA damaged –> repair or apoptosis - regulated by TP53

Question 5

What types of molecule regulate the cell cycle?

Answer 5

Heterodimeric protein kinases composed of:

1. Cyclins - regulatory sub-unit, no catalytic activity
2. Cyclin-dependent kinases (CDKs) - activated by partner cyclin, forms catalytic sub-unit

Question 6

How do serine/threonine protein kinases function?

Answer 6

Phosphorylate target proteins - adds negative charge –> conformational change –> change in function (enzyme activity, cellular location, association with other proteins)