Final exam

Question 1

Regulation of Cell Division

Answer 1

Eukaryotic cells use growth factor to progress to S phase. Prokaryotes constantly divide unless the environment is poor

Question 2

Interphase

Answer 2

G1, S, G2 phases
Gap 1, 11hrs, replication proteins and histones created, growth
Synthesis, 8hr, Monads are duplicated semiconservatively
G2, 4hrs, prepares MTs, myosin, MFs, duplicates centrosome

Question 3

Mitosis

Answer 3

1 hr long
Prophase - chromosomes condense, MTs form, chromosomes begin to separate
Prometaphase - Mitotic spindle fibers connect to kinetochores, nuclear envelope and lamina breakdown
Metaphase - chromosomes line up at metaphase plate, MTs grow in positive direction, kinesin binds to kinetochore MTs at centromeres of chromosomes
Anaphase A - monads move to centrosomes MTOCs, MTs shrink, dynein on KC-MTs, cohesin breakdown
Anaphase B - centrosomes move towards PM, astral MTs reel the centrosome with dynein. Polar MTs use kinesin to push the centrosomes apart
Telophase - nucleus reforms, chromosomes decondense, MTs disassemble, contractile ring with myosin and MTs forms for cytokinesis.

Question 4

Cell Cycle Checkpoints

Answer 4

G1 CP - checks for growth factor, cells without move to G0 instead of S. Checks for large enough cell size, needed proteins, and damaged DNA.
S CP - after replication, determines if DNA is damaged, if so then forces cell death
G2 CP - checks if cell is large enough, if needed proteins are present, and if DNA is damaged.
M CP - between metaphase and anaphase, checks for proper spindle assembly and chromosome alignment, if kinetochores are attached to MTs.

Question 5

Growth Factor in replication

Answer 5

Sends signals in cells to cause replication. Cyclin and collagen are transcribed as a result of their signal. GF–>RTK/GPCR->Ras/Raf/Mek/Erk->nucleus->txn of collagen and cyclin

Question 6

Cell cycle regulation with cyclin concentration

Answer 6

Cyclin cycles to control the activation of Cyclin-Dependent Kinase CDK. Late in S phase, cyclins begin to rise until M phase entry, activating CDKs. Cyclin levels lower in late mitosis until G1 entry.

Question 7

Cyclin-Dependent Kinases

Answer 7

Activated when cyclin concentration is high. Concentration of CDK does not change, but is activated as needed. CDK phosphorylates cellular components when activated.
CDK phosphorylates the nuclear lamina to cause its breakdown using intermediate filament lamins.
Condensin is phosphorylated to tighten chromatin into heterochromatin, condensing chromosomes.
MT proteins are phosphorylated to create the mitotic spindle.
Golgi Matrix proteins are phosphorylated to fragment the Golgi.
Once CDK is inactive, phosphatases are activated, removing phosphate residue. The hydrolysis causes the reversal of CDK processes, like reformation of the nucleus.