introduction

Question 1

what is cells cycle?

Answer 1

the sequence of events which includes the duplication of the genome, synthesis of its constituents and finally division into two daughter cells.

Question 2

how long does the cell cycle last (period)?

Answer 2

it depends on the organism.

eg: yeast - 90min, human cell - 24hrs

Question 3

what are the two phases under in cell cycle?

Answer 3

1) interphase / resting phase:
- replication of DNA
- synthesis of organelles
- takes more than 95% of the cell cycle
2) mitotic phase/division phase :
- cell divides
- less than 5% of the cell cycle

Question 4

what are the three phases under interphase?

Answer 4

1) G1 phase
2) S phase
3) G2 phase
4) G0 phase(extended)

Question 5

what do G and S stand for?

Answer 5

G - growth/gap

S - synthesis

Question 6

explain the G1 phase?

Answer 6

• it is a post-mitotic phase
• cell duplicates most of the cell organelles
• cell synthesises :
  1) protein , @) ATP, 3) amino acid , 4) nucleotides 5) RNA etc.
• this phase is shorter in cells that frequently divide
• this phase is longer in cells that divide less frequent;y

Question 7

what is a major checkpoint?

Answer 7

• present betweenG1 and S phase

- produces G1 cyclic and CDC 2 kinase protein

Question 8

explain the S phase?

Answer 8

• on chromatid chromosome duplicates to form two chromatid chromosome with 2 sister chromatids
• no. chromosomes remain the same
• amount of genetic material increases
• synthesis of histone proteins
• centriole duplication occures

Question 9

explain the G2 phase?

Answer 9

• pre mitotic phase
• synthesis of mitochondria, chloroplast and Golgi body
• tubuin protein syntheis
• RNA synthesis

Question 10

what is the minor checkpoint?

Answer 10

_ present between mitotic and G 2 phase

- mitotic cyclin and CDC2 kinase protein

Question 11

explain the G0 phase?

Answer 11

cell enters a quiescent stage and are metabolically active at this phase but they do not proliferate unless brain and heart cells are asked to do so.