Cell Cycle (CH 19)

Question 1

stages of cell cycle

Answer 1

Gap1, S-phase, Gap 2, Mitosis

Question 2

Gap 1

Answer 2

cell grows in size, synthesize RNA & proteins needed for DNA synthesis

Question 3

S-phase

Answer 3

chromosome replication, each copy connects as sister chromatids

Question 4

Gap 2

Answer 4

cell prepares for mitoses

Question 5

Mitosis

Answer 5

beginning: nuclear membrane breaks down, retracts to ER, golgi breaks into vesicles, microtubles break down and reassemble into mitotic apparatus, and spindle pole forms and associate with kinetochore
end: sister chromatids move to ends of cell, mitotic spindle disassembles

Question 6

cyclin

Answer 6

regulatory subunit;
G1 or
B-type (cyclin B&A)- have destruction box w/ APC/C Cdh 1

Question 7

CDK

Answer 7

cyclin dependent kinase that phosphorylates proteins

Question 8

Mid G1 cyclin-CDK

Answer 8

activate transcription factors that induce gene expression needed for DNA synthesis and S-phase cyclin and CDKs
(Cyclin D-CDK4 and Cyclin D-CDK6)

Question 9

Late-G1 cyclin-CDK

Answer 9

phosphorylate inhibitors to activate SCF (ubiquitin protein ligase - leads to inhibition of inhibitors to release S-phase cyclin-CDKs)
(Cyclin E-CDK2)

Question 10

S-phase cyclin-CDK

Answer 10

phosphorylate proteins, initiate DNA replication, and inhibit reassembly of complexes to ensure single replication
(Cyclin A-CDK2)

Question 11

Mitotic cyclin-CDK

Answer 11

activated by dephosphorylation; phosphorylates substrates
(Cyclin A-CDK1
Cyclin B - CDK1)

Question 12

role of Rb and E2F proteins in cell cycle progression

Answer 12

Rb (retinoblastoma) - blocks cell cycle progression by inhibiting activity of E2F transcription factors. Hypophosphorylated Rb binds E2F, blocking it from binding to promoter. In
Mid G1 CyclinD-CDK4/6 phosphorylate Rb. In Late G1: CyclinE-CDK2 hyperphosphorylates Rb, releasing E2F and allowing gene transcription.
E2F regulates expression of genes needed for DNA replication, cyclin-CDKs, etc.

Question 13

early response genes

Answer 13

induced by transcription factors already present in the cell (CREB, SRF, etc)

Question 14

late response genes

Answer 14

require new protein synthesis; dependent on transcription and translation of early response genes (include transcription factors & Cyclin-CDKs needed for cell cycle progression)

Question 15

APC-mediated degradation of mitotic cyclins

Answer 15

Late anaphase:
APC/C is active (bound to Cdh1). APC/C polyubiquitinates mitotic cyclin (A/B) for degragation by proteasome. Kinase activity declines to trigger telophase. G1-cyclin CDK phosphorylates Cdh1, does not associate with APC/C making it inactive.
Prophase:
Mitotic cyclin is synthesized. Cdc14 removes phosphate from Cdh1, allows to activate APC/C.

Question 16

APC

Answer 16

Anaphase-Promoting Complex

Question 17

APC promotion of sister chromatid separation

Answer 17

APC, guided and bound by protein Cdc20, ubiquitinates securin. This releases separase to cleave Scc1, allowing sister chromatids (held together at Smc) to dissociate.

Question 18

cell cycle checkpoints and regulation

Answer 18

Unreplicated DNA: ATR-Chk1
Spindle-assembly: Mad2
Spindle-position: Cdc14
DNA-damage: ATM/R