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37 Cards in this Set

  • Front
  • Back
What chromosomes are involved in Robertsonian translocation?
acrocentric chromosomes 13-15, 21-22
What makes translocations special?
they involve two chromosomes

inv, del, dup, i, etc. occurs within one chromosome
Why is regulation of Nuclear import important?
partitioning of factors for timed interactions
1. transcription regulation
2. cell cycle control
3. RNA splicing (speed of splicing determines what is exported).
What accounts sfor the great variability in tissue proliferation rates?
G0 phase, because cells can stay in it for as long or as short as they want.
in s phase what is the time scale and order for genome replication
-early replicating - transcriptionally active genes

-late replicating - inactive genes and non coding sequences
when do centrosomes duplicate (what phase?)
-duplicate during s/G2
and separate during M phase
When talking about cdk and cyclin what kind of subunits are they?
-cdk the catlytic subunit
-cyclin the regulatory subunit
What is the molecular mechanism of the restriction point
pRB binds to the Tx factor E2F and suppresses transcription

cdk4/cyclinD and cdk2/cyclin E phosphorylate pRB, a phosphorylated pRB doesn't bind E2f, and so genes can be transcribed
What are the two mechanisms by which pRB represses transcription (at the restriction point)
1. unphosphorylated pRB binds to E2F and blocks its transcriptional activation domain

2. pRB/E2F complex binds to the promoter region of DNA, suppressing transcription by recruiting histone deacetylases and DNA methylators
E2F promoters regulate the transcription of genes necessary for DNA replication
what inhibitory protein families regulate cdk expression
-ink family
name members of the ink family
p15, p16, p18, p19
name members of the cip/kip family
p21, p27, p57
ink family
suppresses D complexes
ink family
cyclin D
ink family
suppresses cyclin D complexes
ink family
suppresses cyclin D complexes
cip/kip family
suppresses cyclin A & E complexes
cip/kip family
suppresses cyclin E & A
cip/kip family
suppresses cyclin E & A complexes
what do ink family members inhibit?
complexes involving cyclin D
what do cip/kip family members inhibit?
complexes involving cyclin E and cyclin A
pRB, where does it regulate?
ThINK at the restriction point!!
what is the mechanism of the G1 phase checkpoint?
1. ATM (or ATF) activation results in p53 phosphorylation
2. active p53, increase p53 levels
3. increase tx of p21, p21 levels increase
4. p21 inhibits cdk2/cyclinE complex
5. The cell is kept in G1 phase becasue of damaged DNA, it cannot pass into the S phase
(further: think that cdk2/cyclin E cannot then phosphorylate pRb, therefore E2F is still inhibited).
what is the mechanism of the G2 phase checkpoint?
1. DNA damage activates ATM or ATF
2. ATM phosphorylates/activates chk1 & chk2
3. Chk1 and 2 phosphorylates CDC25, inhibiting it.
4. CDC25 cannot activate MPF by removing a phosphate group
5. The cell is stuck in G2 and cannot move onto M until the DNA damage is repaired
what is the difference in mechanism between the G1 and G2 checkpoints?
They are both activated by ATM & ATF, but different proteins are effected.

For the G1 checkpoint, think:
p53, p21, inhibits cdk2/cyclin E

For the G2 checkpoint, think:
Chk1, Chk2, p-cdc25, inactive MPF
when is cyclin B produced
Technically during the early S phase
cyclin B is degraded at the onset of anaphase.
Thr 161
the activating site on MPF, that Cdk activating kinase phosphorylates
Thr 14, & 15.
ATP binding sites that are phosphorylated (causes inhibiton of MPF) by the wee 1
How does MPF trigger mitosis
1. causes chromosome condensation (activates condensin)
2. causes phosphorylation of lamins, which causes nuclear envelope break down
3. assists in assembly of the mitotic spindle, by phosphorylating MT associated proteins (MAPs)
a protein that introduces positive supercoils in DNA, this helps in chromosome condensation when cells progress into Mitosis,

condensin is activated by MPF
what is the difference between ATM and ATR?
both proteins activated when there is DNA damage for the G1 and G2 checkpoints
Ionizing radiation activates ATM
UV radiation activates ATR
MPF involvement in anaphase?
activates APC after the cell passes the spindle checkpoint
anaphase promoting complex
-is a ubiquitin ligase
once the cell has passed the spindle checkpoint, APC is activated, it ubiquinates securin, causing it to be degraded
is an anaphase inhibitor

APC polyubiquinates it, causing it to be degraded and promoting cell transition into anaphase.
a protease that cleaves the cohesin (attahments between sister chromatids)
proteins that hold the sister chromatids together, they are cleaved by separase and this initiates anaphase