Mitosis

Question 1

What is mitosis for?

Answer 1

Growth, differentiation and repair.

Question 2

5 stages of mitosis

Answer 2

Interphase, prophase, metaphase, anaphase and telophase.

Question 3

Interphase

Answer 3

G1 phase - organelles are synthesised and the cell grows. 
Synthesis phase (S) - the DNA is replicated. The amount of DNA doubles but the number of chromosomes stays the same. 
G2 phase - organelles grow. The energy stores increase. If a cell is only in interphase for a short amount if time, it is dividing rapidly.

Question 4

Prophase

Answer 4

The chromosomes condense and become visible.
Chromosomes appear as chromatids joined by the centromere.
The nuclear envelope disintegrates.
The nucleolus disappears.

Question 5

Metaphase

Answer 5

Spindle is formed.
Chromosomes attach to the spindle by the centromere.
Chromosomes line up at the equator/centre of the cell.

Question 6

Anaphase

Answer 6

The centromere splits.

The sister chromatids separate to opposite poles of the cell.

Question 7

Telophase

Answer 7

The nuclear envelope reforms.
The spindle disintegrates.
The chromosomes uncoil and become thinner.

Question 8

Viral replication (not HIV replication)

Answer 8

Viruses are classed as non-living as they cannot undergo cell division.
They replicate by attaching to the host cell with the attachment proteins on their surface.
The virus injects nucleic acid into the host cell.
The nucleic acid is combined with the host cells DNA, which starts producing viral components. These are assembled into new proteins.

Question 9

Prokaryotic cell division - Binary fission

Answer 9

The circular DNA molecule replicates and both copies attach to the cell membrane. The plasmids replicate.
The cell membrane grows between the two DNA molecules .
The cell membrane pinches inward between the two DNA molecules, dividing the cytoplasm.
A new cell wall forms between the two DNA molecules.

Question 10

How do cancer cells affect mitosis?

Answer 10

Cancer cells affect the genes that regulate mitosis, by damaging them.
This leads to uncontrollable cell division.

Question 11

How are drugs are used to treat cancer cells?

Answer 11

Drugs usually stop/slow mitosis. This is because they stop the DNA replicating or it stops spindles being made.

Question 12

Role of the spindle in mitosis

Answer 12

To pull the chromatids apart.

For the centromeres to attach to.

Question 13

What does mitosis make?

Answer 13

Two genetically identical daughter cells.