Mitosis

Question 1

Why does mitosis occur

Answer 1

Mitosis occurs because cells need to be produced for growth and repair of tissues, so the cells must divide as cells arise from pre-existing cells

Question 2

Describe what is produced after mitosis

Answer 2

2 genetically identical daughter cells

Question 3

Why is it important that the cells produced in mitosis are identical

Answer 3

So they have the same structure and function as the other cells, to replace the damaged cells

Question 4

Before mitosis, what genetic material is present in the cell

Answer 4

Chromatin

Question 5

Describe what is meant by chromatin

Answer 5

Long, thin threads of DNA

Question 6

Describe what happens during interphase

Answer 6

DNA replicates, and the ell synthesises a lot of ATP

Question 7

What are each ‘leg’ of a chromosome called

Answer 7

Chromatids

Question 8

Why does a chromosome have 2 chromatids

Answer 8

DNA has replicated

Question 9

Describe what is meant by sister chromatids

Answer 9

Chromatids that contain identical genetic material

Question 10

What holds together the 2 chromatids in a chromosome

Answer 10

The centromere

Question 11

What does the centromere do during mitosis. Explain why

Answer 11

• The centromere wll divide, allowing the chromatids to be pulled apart into separate cells
• This ensures hat each cell gets an identical copy of DNA

Question 12

What happens to the separated chromatids at the end of mitosis

Answer 12

The separated chromatids become longer and thinner again, where each new cell has an identical copy of DNA

Question 13

Describe what happens to the DNA during mitosis to ensure that both cells produced are identical

Answer 13

• The DNA replicates during interphase prior to cell division
• The DNA condenses becoming shorter and thicker
• Chromosomes consisting of two identical chromatids held together by a centromere are formed
• The centromere divides and the two chromatids are pulled apart
• The chromatids becomes longer and thinner

Question 14

What are 4 stages of mitosis

Answer 14

• Prophase
• Metaphase
• Anaphase
• Telophase

Question 15

Describe what happens during Prophase

Answer 15

• The nuclear envelope breaks down
• The chromosomes condense
• The spindle fibres are formed by organelles called centrioles, which move to opposite poles (ends) of the cell

Question 16

Describe what happens during metaphase

Answer 16

• The chromosomes align in the middle of the cell
• Spindle firbres attach to the centromere of each chromosome

Question 17

Describe what happens during Anaphase

Answer 17

• The centromeres divide
• The spindle fibres contract (which requires energy from ATP)
• The chromatids separate and are pulled to opposite poles

Question 18

Describe what happens during Telophase

Answer 18

• The spindle fibres disintergrate
• The nuclear envelope begins to reform
• The chromosomes become longer and thinner once more

Question 19

Describe birary fission in bacteria (3)

Answer 19

• Circular DNA replicates
• Plasmids replicate
• Cytoplasm divides to produce daughter cells

Question 20

Suggest and explain how two environmental variables could be changed to increase the growth rate of these cells.

Answer 20

• Increase concentration of glucose
• This increases the rate of respiration
• Increase the temperature
• This increases enzyme activity