14. The genetics of the cell cycle Flashcards
how do yeast cells divide
budding
what is the first control point called in yeast called
START
who won the Nobel prize for identifying genes involved in the cell division
Lee Hartwell
describe temperature sensitive mutant studies
temp. sensitive mutants could grow at temps up to 25 deg.C
addition of a functional copy of the gene rescues the mutant when temperature is too high
what process was used to test the temp. sensitive mutants
complementation
how were functional genes added to the mutants
wild-type yeast genome is digested and ligated into plasmids
what gene allows survival of cells at higher temperatures
cdc28
what is cdc28 a component of
S-phase promoting factor
a CDK
at high temperatures. what happens to temp-sensitive mutants, in regards to cyclin
it dissociates = no growth - cannot move from the G1 to S phase
what do cdc28 mutant cells transformed with G1 cyclin plasmids show
functional complex
= progression through mitosis
in S. pombe, what does the size of the cell show
shows what phase the cell is in - it is intrinsically linked
what is complementation
experiments that use mutants to see whether the addition of certain genes can recover cell growth in specific conditions
what causes the arrest of S. pombe during fission, at what stage
cdc mutants
G2/M arrest
what is the difference between budding and fission in yeast in terms of control point
budding= major control point G1/S phase
fission = major control point G2/M phase
what is the difference between budding and fission in yeast in terms of cell size
budding = produces a bud
fission = intrinsically linked to cell length, the longer the cell the further through fission it is
give an example of a yeast that does fission
schizosaccaromyces pombe
give an example of a yeast that does budding
saccharomyces cerevisiae
cdc28 is another term for what
CDK1
what is the structure of CDK s in eukaryotes
highly conserved
S. pombe ts mutants can also be rescued by cdc28, and what else?
what does this show?
human CDK1
structurally and functionally conserved in eukaryotes
what happens to cdc2 knockout cells
they continue to grow, but are unable to enter mitosis
CANNOT MOVE FROM G2 INTO S PHASE
what 2 genes activate MPF
Wee1
Cdc25
what regulates CDK activity
cyclin binding
phosphorylation
what is Wee1
a kinase
what is Cdc25
a phosphatase
when does cyclin expression occur
late S/G2 phase
what is required to activate Cdc2
phosphorylation at T161 by CAK
what does CAK stand for
CDK activating kinase
for full activity of MPF, what else must happen to Cdc2
dephosphorylation of tyrosine 15 by Cdc25
how does Wee1 inhibit MPF
by inhibitory phosphorylations of tyrosine 15
what happens if there is excess wee1 and deficit of cdc25
large cells = no mitosis
what happens if there is deficit of wee1 and excess cdc25
small cells = innapropriate mitosis
