Cell Division And Cycle

Question 1

Cell fusion- Rao and johnson

Answer 1

Merged cells
S+ G1 = S
G2 + M = M

Question 2

Discovery of MPF

Answer 2

Cytoplasm from M phase triggers M phase in a G2 cell

Maturation promoting factor

Question 3

Discovery of cyclin

Answer 3

MPF follows the same peaks as Cyclin B during cycle

Question 4

Cdc mutants in yeast

Answer 4

Budding yeast mutants
Temperature sensitive for cycle progression
At restricted temperatures were either very long or very short
Concluded Cdc2 is the major controller of G2/M

Question 5

Maller- purification of MPF

Answer 5

MPF = cdc2/cdk1 (protein kinase) + cyclin B (regulatory)

Question 6

Activation of MPF

Answer 6

Cyclin B + cdk1 -> inactive MPF
Wee1 phosphorylates Y15
CAK phosphorylates T161
Cdc25 dephosphorylates Y15 -> active MPF

Question 7

Cdk1 controls G2
What are its substrates
4

Answer 7

Nuclear lamins
Nucleolin
Histones
GM130 (Golgi matrix protein)

In yeast, cdk1 also controls G1

Question 8

What controls G1/S in mammals and yeast

Answer 8

Yeast- cdk1
Mammal- cdk2 associated with cyclin D and cyclin E

Cdk1 also controls G1 in yeast with cln1,2 and 3

Question 9

Substrates of cdk2/cyclin D

Answer 9

Transcription factors that regulate the genes of DNA synthesis
Cyclin D and E - regulated by cyclin dependent kinase inhibitors, p21, p27, p15, p16, p19

Question 10

P53

Answer 10

Gene for li-fraumeni syndrome (high cancer)
Moderate UV exposure repaired by p21
Severe exposure -> death

Question 11

P27

Answer 11

Monitors cell growth
Induces by external signals and cell to cell contact
P27 knock out mice are larger due to more cells
P27 blocks catalytic site of Cdk preventing ATP binding

Question 12

P57Kip2

Answer 12

Beckwith Wiedemann syndrome
Overgrowth of organs -> cancer
Same locus for IGF2
IGF2- knock out mice reduced in size
Only one of 2 of the IGF2 parental copies is expressed (father)

Question 13

DNA damage causes arrest in G2

Answer 13

Rad3+ -> activates Chk1
Chk1 keeps Cdk1 phosphorylated and stops G2->M

In humans this is ATM causing cdc25 to stop G1 -> S

Question 14

5 phases of cell division

Answer 14

S phase- DNA replication
M phase- cell division (mitosis and cytokinesis)
G1- gap 1 is cell big enough, neighbouring cells
G2- gap 2 is DNA correct
G0- non dividing

Question 15

ATM definition

Answer 15

Ataxia- staggering gate
Telangiectasia- dilate blood vessel in eye
Mutated
Radiosensitivity and predisposition to cancer

Question 16

Breast cancer susceptibility genes

Answer 16

BRCA1 and BRCA2

5-10% of Breast cancer

Question 17

Oncogenesis

Answer 17

Most tumours aneuploid room mitosis
Chromosome segregation error
In meiosis leads to trisomy 21,9,13,18

Question 18

Role of cdc in chromosome segregation

Answer 18

Free kinetochore- mad2/cdc20 bound
Attached kinetochore- mad2/cdc20 released
Cdc20 activates APC -> esp1 free
Esp1 is a seperase -> chromatids seperate

Inhibition of psd1 (bound to esp1) triggers anaphase as esp1 is then free

Question 19

Budding yeast mutants unable to seperate sister chromatids

Answer 19

Smc1 + smc3 -> ring that holds DNA
Scc1 closes ring
Cleavage of Scc1 by Esp1 (determined by APC)
Ring opens and releases DNA
Chromatids separate