Lecture 4 Flashcards
what is the order of the cell cycle
- G1 phase
- S phase DNA replication
- G2 phase
- M phase mitosis and cytokinesis
during what stage does DNA replication happen
interphase
when does mitosis happen
M phase
when does cytokinesis happen
m phase
what are the stages of mitosis
- prophase
- prometaphase
- metaphase
- anaphase
- telophase
what is comprised within interphase
- G1
- S
- G2
what does flank mean
on either side
true/false the cell cycle is present and regulated in all organisms
true
during which stages does cell growth occur
at all phases EXCEPT during mitosis
how much of the cell cycle does mitosis take up
5-10%
true/false lots of cells are in G0
true
M phase is flanked by which 2 phases
G1 and G2
when are the 3 major checkpoints in the cell cycle
- start checkpoint in G1/S
- G2/M checkpoint
- metaphase/ anaphase checkpoint
what does the G1/S checkpoint look for
is environment favourable?
what does the G2/M checkpoint look for
- is all DNA replicated
- is environment favourable
what does the metaphase/anaphase checkpoint look for
are all chromosomes attached to the spindle
if a cell passes the G1/S checkpoint, what can it do
enter cell cycle and proceed to S phase
if a cell passes the G2/M checkpoint, what can it do
enter mitosis
if a cell passes the metaphase/anaphase checkpoint, what can it do
trigger anaphase and proceed to cytokinesis
what do kinases do
add phosphate groups
true/false the kinase activity of each type of cyclin-Cdk complexes change as the cell progresses through the cell cycle
true
true/false the level of Cdks vary throughout the cell cycle
- false
- they remain relatively constant
- they just bind more when the levels of cyclins go up
true/false the level of cyclins vary throughout the cell cycle
true
where was the cell cycle originally studied
in yeast
what do G1-cyclins do
help coordinate growth of cells during cell cycle
what do G1/S-cyclins do
- bind Cdks in late G1
- commits cell to “START” and DNA replication
what do S-cyclins do
- binds Cdks soon after “START”
- stimulates chromosome duplication
- controls early mitotic events
what do M-cyclins do
promotes the entry of cells into mitosis
what is unique about Cdk proteins in yeasts
- they have a single type
- Cdk1
- controls all the stages of the cell cycle by chnaging diff cyclin partners at the diff stages
true/false a single molecule of Cdk exists in yeast
- False
- single type not molecule
the most common control of cdk activity is what
phosphorylation/ dephosphorylation
what are the 2 parts in cdk2 activation
- binding with cyclin A partially activated cdk2
- phosphorylation of T-loop by CAK fully activated cdk2
what happens if the inhibitory site in the M-cyclin/Cdk complex is phorphorylated by Wee1 kinase
cdk activity is inhibited
what happens if p27 binds to a cyclin-Cdk complex
inhibits the complex
what is p27
a CKI protein
how does p27 inhibit the cyclin-cdk complex
- binds to both the cyclin and the cdk
- this distorts the active site
- it also inserts into the ATP-binding site, inhibiting enzyme activity
The active cyclin–Cdk complex is turned ______ (off/on) when the kinase Wee1 phosphorylates two closely spaced sites above the active site.
off
true/false you can control the cell cycle by degradation of key proteins
true
how is APC/C activity changed throughout the cell cycle
by changes in its association with Cdc20
cyclin D pairs with which cdk
- 4
- 6
cyclin E pairs with which cdk
2
cyclin A pairs with which cdk
- 2
- 1
cyclin B pairs with which cdk
1
