Cell Cycle Flashcards
How do division frequencies differ?
embryo - 20 mins
skin cells - frequently
liver cells - mainly G0 (retain ability to divide and infrequently)
nerve and muscle cells - permanent G0 (never divide again!)
How can we test that there is a control mechanism for the cell cycle?
Fuse an S and G1 phase cell
S phase nucleus will continue replication
G1 instructed to enter S phase
Fuse S and G2
G2 NOT forced into S phase.
How synchronous are early frog embryos?
12 synchronous cycles after IVF.
What studies have been done with humans and MPF?
Extract from mitotically arrested human cells also induces meiosis in oocytes.
What is an MPF?
cyclin bound to CDK?
How do unattached kinetochores differ and what is the result?
They display Mad2 and Bub1 on kinetochores even when on metaphase plate.
This activates formation of MCC.
What is the SAC?
active signal produced by improperly attached kinetochores.
What is the anaphase promotion complex and how is it activated? What are the other two?
E3 ligase
ubiquitinates cyclin B
activated by;
cdc20 in mid mitosis
cdh1 in late mitosis to early G1
MDM2 and SCF.
What two diseases are caused by faults surrounding p53?
ATM - inheriting mutant ATM which prevents repair of Dsbs
Li-Fraumeni - mutant p53 inherited and cancer develops early.
What cyclins are involved in the restriction point?
CDK4/6-CyclinD hypophosphorylates Rb
CDK2-CyclinE hyperphosphorylates Rb.
(E2F now released and can activate transcription of proteins driving S phase) .
What are the roles of;
P53
P21
ATM
Activates transcription of genes involved in cell cycle, repair and apoptosis (cell pauses to repair or carries out apoptosis)
Inhibits S phase cyclins.
Phosphorylation p53 so can’t bind MDM2
What proteins are involved in S phase and what drives their transcription?
DNA polymerase
Thymidine kinase
Cdc6
E2F
How is Rb related to cervical cancer?
Human papilloma virus
E7 protein degrading Rb encoded in HPV which becomes ubiquitinated.
