3.2.2 Cell Cycle

Question 1

Do all cells retain the ability to divide?

Answer 1

No

Question 2

What happens in interphase?

Answer 2

Gap 1
DNA synthesis
Gap 2

Question 3

What is the prophase stage of mitosis?

Answer 3

• chromosomes become visible -> condense and become short and fat
• centrioles move the poles
• nuclear envelope breaks down
• nucleolus dissapears
• spindle fibres develop

Question 4

What is metaphase in mitosis?

Answer 4

• the chromosomes line up along the equator

- the spindle fibres attach to the centromeres

Question 5

What is anaphase in mitosis?

Answer 5

• the spindle fibres contract, pulling the centromere

- this causes the separation of each sister chromatid to opposite ends of the cell

Question 6

What is telophase in mitosis?

Answer 6

• chromatids reach the opposite poles on the spindle
• they uncoil, becoming long and thin
• nuclear envelope forms around each group of chromosomes, there are now two nuclei

Question 7

What is cytokinesis?

Answer 7

the division of the cytoplasm, creating two separate cells
Made by constriction from the edge of the cell

cell membrane forms a cleavage furrow that eventually pinches the cell into two parts, each part containing its own nucleus

Question 8

What is binary fission?

4 steps

Answer 8

1) circular DNA and plasmids replicate
- the main DNA loop is only replicated once, however plasmids can replicate multiple times

2) cell gets bigger and DNA moves to either side
3) the cytoplasm begins to divide

4) cytoplasm divides and two daughter cells are produced
- each daughter cell has one copy of the circular DNA but can have a variable number of plasmid copies

Question 9

How to viruses replicate?

Answer 9

viruses use their attachment proteins to bind to complementary receptor proteins on the surface of host cells.

they then inject their DNA or RNA into the host cell

the host cell then replicated the viral particles

Question 10

What is a somatic cell?

Answer 10

A typical body cell with twice the number of chromosomes as the gamete

Question 11

How do you calculate the mitotic index?

Answer 11

Mitotic cells
—————– X 100
Total cells

Question 12

What happens in Gap 1?

Answer 12

• the cell grows and organelles and proteins are made

- cell carries out normal functions

Question 13

What happens in Gap 2?

Answer 13

• cell keeps growing

- proteins needed for division are made

Question 14

What happens in S1 (synthesis) in interphase?

Answer 14

-cell replicates it’s DNA

Question 15

How is a tumour formed?

Answer 15

a tumour is formed is formed when there is uncontrollable replication/cell division

Question 16

What is cancer?

Answer 16

cancer is a tumour that invades surrounding tissues

Question 17

Why is mitosis important?

Answer 17

it is important as it produces daughter cells that are genetically identical to the parent cell

• growth
• repair
• reproduction