cell division - eukaryotic cell cycle

Question 1

why cant nerve cells divide by mitosis ?

Answer 1

they lack centrioles
memory and learning is based on new connections between neurones in the brain and these would be destroyed during cell division

Question 2

why do red blood cells never enter the actve part of the cell cycle ?

Answer 2

once they ahve matured, they lack a nucleus and other organelles to maximise the amont of heamoglobin in their cytoplasm
they must be continually produced from stem cells in the bone marrow as they only last 3 months
these cells are stuck in the G0 phase permanently

Question 3

what is the cell cycle ?

Answer 3

highly ordered sequence of events

resulting in cell division

formation of new cells

Question 4

what is the first major event of the cell cycle and what does it consist of ?

Answer 4

interphase and cells are only prepearing to divide. it has 3 parts:
G1
S phase
G2

Question 5

what is G1 ?

Answer 5

growth 1 - where organelles repllcate and cells increase in size
protiens are synthesised

Question 6

what is S phase ?

Answer 6

synthesis - dna is replicated within the nucleus by semi conservative replication

Question 7

what is G2 ?

Answer 7

growth 2 - cells continue to grow in size, atp produced by respiration and replicated dna is checked for errors

Question 8

what happens if cells specialize ?

Answer 8

they lose the ability to divide and enter a phase called G0, where they stop going through the cycle

Question 9

when can cells only divide ?

Answer 9

it has grown to the correct size
replicated dna is error free
chromosomes are in the correct position during mitosis

Question 10

what are checkpoints ?

Answer 10

control mechanisms of the cell cycle
monitor and verify weather the processes at ech phase have been completed correctly
prevents uncontolled cell division which could lead to cancer

Question 11

why is S phase rapid ?

Answer 11

to reduce damage to exposed dna bases