2.1.6 Cell division

Question 1

State what the cell cycle is and outline its stages

Answer 1

• Regulated cycle of division with intermediate growth periods
• Interphase
• Mitosis or meiosis (nuclear division)
• Cytokinesis (cytoplasmic division)

Question 2

Online what happens during interphase

Answer 2

• G1: cell synthesis proteins for replication
• S: DNA replicates
• G2: organelles divide

Question 3

What is the purpose of mitosis

Answer 3

Produces 2 genetically identical daughter cells for:
- Growth
- Cell replacement/ tissue repair
- Asexual reproduction

Question 4

Name the stages of mitosis

Answer 4

P- prophase
M- metaphase
A- anaphase
T- telophase

Question 5

Outline what happens during prophase

Answer 5

• Chromosomes condense becoming visible
• Centrioles move to opposite poles of cell and mitotic spindle fibres form
• Nuclear envelope and 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 energy from ATP hydrolysis
  -Sindle fibres contract and centromeres divide
• Sister chromatids separate into 2 distinct chromosomes and are pulled to opposite poles of cell
• Spindle fibres break down

Question 8

Outline what happens during telophase

Answer 8

1. Chromosomes decondense, becoming invisible again
2. New nuclear envelope 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 dont progress to next stage of cycle