Cell Cycle 1 Flashcards
what is the cell cycle
process by which the cell duplicates its contents and then divides into 2 daughter cells
describe cell cycle outcome for multi and unicellular organisms
uni=two complete new organisms
multi=replacing cells that die
at its most fundamental what does the cell cycle involve
high fideloty duplication of genetic material
accurate distribution of chromosomes into daughter cells
what is the s phase
period during which chromosomes are replicated
what is the m phase
period where replicated chromosomes are segreagted -mitosis- and cell divieds- cytokinesis
what process occurs after s phase
sister chromatids held together by sister chromatid cohesion
what happens when loss of sister chromatid cohesion
at metaphase anapahse tansition results in sister chromatids being pulled in opposite directions by spindles
what is the purpose of gap phasaes
allow cell to grow and monitors internaland external environment
what happens if conditions are not favourable for G1-S transition
cells enter specialised resting state called G0
how is cell cycle progression controlled
complex network of regulatry interactions
what are complex network of regulatory interactions
control cell cycle progression and include biochemical switched that ordered toensure cell cycle events take place in correct order
what are checkpoints
ensure later events do no take place until earlier events are satisfactory completed
what are conditional lethal mutants in budding yeast
inactivate genes without killing
where do the three major regulatory points occur
G1-s
G2-M
metaphase -anaphase
describe the regulatory point at G1-S transition
allows entry to cell cycle and proceed to S phase
start transition
describe regulatory point at G2-M phase
is all DNA replicated?
allows entry into mitosis
describe regulatory point at metaphase-anaphase transition
are all chromosomes attached to spindle
triggers anaphase to progress to cytokinesis
how is progression through cell cycle controlled
by CDK complexes
wat are CDK complexes comprised of
catalytic subunit
regulatory subunit
what is the catalytic subunit on CDK complexes
protein kinases called CDKs and are present at constant level throughout cycle
what are the regulatory subunits on CDK complexes
cyclins and undergo a cycle of synthesis and deconstruction during each cycle
how were CDKs first identified
by genetic analysis of budding yeast
budding yeat CDC28 proteins are CDK enzymes (CDK1)
inactivation lead to cell cycle arrest
what are the three essential classes of cyclin protein
G1/S cyclins
s-phase cyclins
m-phase cyclins
what are G1/S cyclins
actiavte CDKs in late G1
resulting in commitment to entry to S-phase
this is called ‘start’
what are S-phase cycline
interact with CDKs just after start and stimulate DNA replication
what are M-phase cyclins
activate CDKs to drive mitosis
why are there different CDK-cyclin complexes at each stage
as well to activating their cognate CD enzyme, cyclins confer substrate specificity on CDK
how is cyclin dependent kinase activated
cyclin binding moves t loop preventing it blocking enzymes active site
a second kinase called CAK phosphorylated a serine or threonine in t loop to further enhance activity
how is M-CDK activity inhibited
by Wee 1 protein kinase and they phosphorylate CDK1 on two neighbouring amino acids near active site
how is M-CDK inhibition relieved
CDC25 phosphoprotein phosphotase removes phophates
