2.1.6 cell division

Question 1

define mitosis

Answer 1

a type of cell division which produces 2 identical a copies of the cell used for growth and repair
asexual reproduction

Question 2

what are the main phases of mitosis

Answer 2

interphase - (G1, S, G2)
prophase
metaphase
anaphase
telophase
cytokinesis

Question 3

describe what happens during interphase

Answer 3

cells are not continuously dividing - spend most time in interphase
involves growth, producing hormones, preparing to divide, protein synthesis, mitochondria + chloroplasts divide, DNA replicates and checked for errors
cells aren’t actively dividing

Question 4

explain what happens in the G1 phase

Answer 4

cells grow bigger + replicate organelles
lots of protein synthesis occurs
cell size increases

Question 5

explain what happens during S phase

Answer 5

cells replicate DNA in the nucleus

Question 6

explain what happens during G2 phase

Answer 6

cells continue to grow
energy stores are increases
replicated DNA is checked for errors

Question 7

describe the structure of chromosomes once DNA has replicated

Answer 7

each chromosome is made of 2 sister chromatids
connected by centromere

Question 8

explain what is meant by G0

Answer 8

phase when cell leaves the cell cycle
can be temporary or permanent
called senescent cells
can happen due to
- differentiation
- damaged DNA
- increased number of cells
can be stimulated to reenter cell cycle

Question 9

explain how differentiation makes a cell enter G0

Answer 9

cells specialise to carry out a function
cannot divide anymore
will NEVER enter cell cycle again

Question 10

explain how damaged DNA makes a cell enter G0

Answer 10

cell’s no longer viable
enters permanent cell arrest (G0)
becomes senescent

Question 11

explain how increased number of cells makes a cell enter G0

Answer 11

no of cells in your body increases as you age
more senescent cells in body
can be linked to age related diseases (arthritis, cancer)

Question 12

how do cells control the process of cell division

Answer 12

have checkpoints at various stages
to check if each process has been completed accurately + prevent errors/mutations

Question 13

what happens at the G1 checkpoint

Answer 13

end of G1 phase
ensure cell has right size, no damaged DNA
if cell doesn’t meet requirements it can begin S phase (DNA replication)
if not = enters G0

Question 14

what happens at the G2 checkpoint

Answer 14

end of G2 phase
before mitosis phase
check for cell size and damages in DNA replication

Question 15

what happens at spindle assembly check point

Answer 15

during metaphase
check that all chromosomes should be attached to spindles + aligned (by centromere) if not - mitosis cannot proceed