Cell Division

Question 1

Interphase

Answer 1

G1, S and G2
Cell grows, centrioles and sub cellular structures replicate

Question 2

Prophase (mitosis)

Answer 2

Chromosomes supercoil and held together by centromere
Nucleolus and nuclear envelope disintegrate

Question 3

Metaphase

Answer 3

Centrioles reach the pole and chromosomes line up across equator. Attached by their centromere to the spindle

Question 4

Anaphase

Answer 4

Chromosomes split at the centromere, sister chromatids pulled apart

Question 5

Telophase

Answer 5

Chromatids reach poles and uncoil
Spindle fibres disintegrate and nuclear envelope reforms

Question 6

Cell cycle checkpoints

Answer 6

1. G1 checks cell size, DNA damage nutrients and growth factor
   G2. Checks cell size and dna damage
   S. Checks chromosomes are attached to the spindle fibres correctly

Question 7

Causes of variation in meiosis

Answer 7

1. Crossing over (prophase 1)
2. Independent assortment of chromosomes (metaphase 1)
3. Independent assortment of chromatids (metaphase 2)
4. Mutations ( dna replications)
5. Random fertilisation