1.5b The cell cycle

Question 1

What does the cell cycle consist of?

Answer 1

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

Question 2

Interphase

Answer 2

The 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 3

Mitotic Phase

Answer 3

The mitotic phase involves mitosis and cytokinesis.

Question 4

Mitosis

Answer 4

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

Mitosis consists of prophase, metaphase, anaphase, and telophase.

Question 5

Prophase

Answer 5

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 6

Metaphase

Answer 6

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

Question 7

Anaphase

Answer 7

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

Question 8

Telophase

Answer 8

The chromosomes decondense and nuclear membranes are formed around them.