Mitosis

Question 1

State what the cell cycle is and outline its stages

Answer 1

Regulated cycle of division with intermediate growth periods

1. Interphase
   2.mitosis or meiosis (nuclear division)
   3.cytokinesis (cytoplasmic division)

Question 2

What happens during interphase?

Answer 2

G1: cell synthesises proteins for replication e.g tumbling for spindle fibres & cell size doubles
S: DNA replication=chromosomes consist of 2 sister chromatids joined at a centromere
G2:organelles divide

Question 3

What is the purpose of mitosis?

Answer 3

Produce 2 genetically identical daughter cells for: growth, cell replacement/tissue repair, asexual reproduction

Question 4

Name the stages of mitosis

Answer 4

1)Prophase
2)Metaphase
3)Anaphase
4)Telophase

Question 5

What happens during prophase?

Answer 5

1)chromosome condense, becoming visible
2)centrioles move to opposite poles of cells & mitosis spindle fibres form
3)nuclear enevelope & nucleolus break down= chromosomes free in cytoplasm

Question 6

Outline what happens during metaphase

Answer 6

Sister chromatids line up at cell equator, attached to the mitotic spindle by their centromeres.

Question 7

Outline what happens during anaphase

Answer 7

Requires ATP from ATP hydrolysis
1)spindle fibres contract= centromeres divide
2) sister chromatids separate into 2 distinct chromosomes & pulled to opposite pole of the cells (looks like V shapes casing each other)
3)spindle fibres break down

Question 8

Outline what happens during telophase

Answer 8

1)chromosomes become invisible again
2) new nuclear envelopes form around each set of chromosomes= 2 new nuclei, each with 1 copy of each chromosome

Question 9

What happens during cytokinesis?

Answer 9

1)cell membrane cleavage furrow forms
2)contractile division of cytoplasm

Question 10

How is the cell cycle regulated?

Answer 10

Checkpoints regulated by cell-signalling proteins ensure damaged cells do not progress to next stage of cycle.
Cyclin-dependent kinase enzymes phosphorylate proteins that initiate next phase of reactions

Question 11

What happens at each checkpoint in the cell cycle

Answer 11

Between G1 & S, cell checks for DNA damage . After restriction point, cell enters cycle.
Between G2 & M cell checks chromosome replication.
At metaphase checkpoint, cell checks that sister chromatids have attached to spindle correctly.