Cell Cycle and Mitosis

Question 1

Describe binary fission in bacteria [3]

Answer 1

• DNA replicates
• Plasmids replicate
• Cytoplasm divides

Question 2

Suggest and explain how two environmental variables could be changed to increase the growth rate of bacteria cells. [4]

Answer 2

• Increased conc. of glucose
• Increased respiration
  OR
• Increased conc. of oxygen
• Increased respiration
  OR
• Increased temp
• Increased enzyme activity
  OR
• Increased conc. of glucose
• Increased respiration
  OR
• Increased conc. of phosphate
• Increased ATP/DNA/RNA
  OR
• Increased conc. of nucleotides
• Increased DNA synthesis

Question 3

Describe and explain the arrangement of the genetic material in prophase. [2]

Answer 3

• Chromosomes become visible
• As they are condensing
  OR
• Chromosomes are at random
• No spindle activity

Question 4

Describe the role of the spindle fibres and the behaviour of the
chromosomes during prophase, metaphase and anaphase. [5]

Answer 4

Prophase
- No spindle activity (not formed yet)
- Chromosomes become more visible as they are condensing
Metaphase
- Spindle fibres attach to the centromere and line up chromatids at the equator of the cell
Anaphase
- Centromere divides
- Spindle fibres pull chromatids towards opposite poles of the cell

Question 5

Why:
- use only the first 5 mm from the tip of an onion root
- press down firmly on the cover slip
[2]

Answer 5

• Most mitosis occurs here
• Spread cells so they can be seen clearly