all cells arise from other cells

Question 1

what are the stages of the cell cycle

Answer 1

1. interphase (longest)
   - DNA replicates semi conservatively leading to 2 chromatids joined at centromere
   - number of the organelles and volumes increase, protein synthesis
2. mitosis
   - nucleus divides
   - to produce 2 nuclei with identical copies of DNA produced by parent cell
3. cytokinesis (shortest)
   - cytoplasm and cell membrane divide
   - to form two genetically identical daughter cells

Question 2

what is the importance of mitosis

Answer 2

growth
replacing cells
asexual reproduction

Question 3

what are the stages of mitosis

Answer 3

prophase
- chromosomes condense become shorter and thicker
- appear as 2 sister chromatids joined by centromere
- nuclear envelop breaks down and spindle fibres form

metaphase
- chromosomes align along equator
- spindle fibres attach to centromeres

anaphase
- spindle fibres contract
- centromere divides
- chromatids pulled to opposite poles

telophase
- chromosomes uncoil and become longer and thinner
- nuclear envelopes reform
- spindle fibres break down

Question 4

draw the stages of mitosis

Answer 4

p - 2 copies of chromosomes in nucleus
m - lined up at equator with spindle fibres attached
a- chromosomes split with spindle fibres pulling them away from each other
t- nucleus divides

Question 5

what happens when cells divide uncontrollably

Answer 5

mitosis is a controlled process
mutations in dna controlling mitosis can lead
to uncontrolled cell division
tumour formed if this results in mass of abnormal cells
cancer is a tumour that can invade surrounding tissue

Question 6

what do cancer treatments aim to do and what do drugs do

Answer 6

control the rate of cell division

some drugs disrupt spindle fibre activity/formation
- chromosomes can’t attach to spindle fibres by centromere
- so chromatids can’t be separated
- no anaphase
- prevents mitosis

some drugs prevent prevent DNA replication during interphase
- can’t make 2 copies of each chromosomes
- prevents mitosis

Question 7

how do prokaryotes replicate

Answer 7

binary fission

replication of circular DNA
replication of plasmids
division of cytoplasm

Question 8

how do viruses replicate

Answer 8

no cell division as acellular non living

attachment proteins bind to complementary receptor protein on surface of host cell
inject nucleus acid into host cell
infected host cell replicates virus particles