3.2.2 All cells arise from other cells

Question 1

Definition of the cell cycle

Answer 1

A regulated sequence of events that occurs between one cell division and the next

Question 2

Is interphase part of mitosis?

Answer 2

No

Question 3

Role of cyclins

Answer 3

Trigger the movement of one phase to the next through chemical signals

Question 4

A cell spends most of its time in which phase?

Answer 4

Interphase

Question 5

3 stages of interphase

Answer 5

1. G1
2. S
3. G2

Question 6

G1 phase

Answer 6

Makes RNA, enzymes and proteins required for growth

Question 7

S phase

Answer 7

DNA in nucleus replicates (through semi conservative replication), each chromosome consists of 2 identical sister chromatids

Question 8

G2 phase

Answer 8

Cells continued to grow, newly synthesised DNA is checked and any errors are repaired

Question 9

Role of centrioles

Answer 9

Produce spindle fibres

Question 10

During G2, what is the function of centrioles?

Answer 10

Duplicate and move to opposite poles of the cell

Question 11

How is cancer generally treated?

Answer 11

Killing dividing cells by blocking parts of the cell cycle, cell division ceases, hence growth of cancer

Question 12

How do cancer drugs disrupt the cell cycle?

Answer 12

• Preventing DNA replication
• Inhibiting the metaphase stage affecting spindle formation

Question 13

Explain what occurs during prophase (3)

Answer 13

Mark in pairs
1. Chromosomes thicken/condense/become visible
AND
2. Chromosomes consist of 2 identical chromatids (called sister centromere)

3. Two centrioles move towards opposite poles of the cell
   AND
4. Spindle fibres emerge from centrioles
5. Nuclear envelope breaks down into vesicles

Question 14

Explain what occurs during metaphase (2)

Answer 14

1. Chromosomes line in the middle of the cell
2. They attach to spindle fibres by their centromeres

Question 15

Describe what occurs during anaphase (1)

Answer 15

Spindle fibres contract and pull sister chromatids to opposite poles of the cell

Question 16

Explain what occurs during telophase (3)

Answer 16

1. Chromosomes arrive at opposite poles and uncoil
2. Spindle fibres break down
3. Nuclear envelope reforms around chromosomes

Question 17

When does cytokinesis occur?

Answer 17

After telophase - final step of cell cycle

Question 18

Describe what occurs during cytokinesis (2)

Answer 18

1. Cytoplasm divides
2. Forms 2 genetically identical daughter cells