Cell Cycle Regulation And Disruption

Question 0

What is cell division control provided by?

Answer 0

CDKs - cyclin dependent kinases

Cyclins - kinase regulatory proteins

Question 1

What does uncontrolled cell division result in?

Answer 1

Cancer

Question 2

What happens if the cell cycle is not initiated by external sequences?

Answer 2

They enter into a prolonged G1(G0) due to lack of G1 cyclins which are destroyed during mitosis

Question 3

What cyclins and CDK make up the complex G1-Cdk?

Answer 3

Cyclin D1, D2 and D3

Cdk4, Cdk6

Question 4

What cyclins and CDK make up the complex G1S-Cdk?

Answer 4

Cyclin E

Cdk2

Question 5

What cyclins and CDK make up the complex S-Cdk?

Answer 5

Cyclin A (SPF)
Cdk2

Question 6

What cyclins and CDK make up the complex M-Cdk?

Answer 6

Cyclin B (MPF)
Cdk1

Question 7

How are Cdk/cyclin complexes regulated?

Answer 7

Cyclic proteolysis
Transcriptional regulation
Inhibitor proteins (CKIs)
Covalent modification (phosphorylation/dephosphorylation)

Question 8

What challenges are present in each cell division?

Answer 8

Must not replicated damaged DNA
Must replicate one, and only one, complete copy of the genome
Must properly segregate a complete copy to each daughter cell

Question 9

What happens at the G1/S checkpoint?

Answer 9

DNA damage assessment

Question 10

What happens at the mid S checkpoint?

Answer 10

DNA replication checkpoint I

Question 11

What happens at the G2/M checkpoint?

Answer 11

DNA replication checkpoint II

Question 12

What happens at the M checkpoint?

Answer 12

Spindle assembly checkpoint

Question 13

What happens at the post M checkpoint?

Answer 13

Polyploidy checkpoint

Question 14

What happens if there is a problem with the polyploidy checkpoint?

Answer 14

Leads to tetraploidization

Question 15

What happens if there are problems at the DNA replication checkpoint?

Answer 15

Leads to telomere dysfunction, rearrangements and amplifications

Question 16

What do tumor suppressors do when they find irreparable damage to DNA?

Answer 16

Send into programmed cell death

Question 17

What are the best described tumor suppressors?

Answer 17

p53 and pRb; both of which are transcription regulators

Question 18

What is p53 considered and why?

Answer 18

It is considered the guardian of the genome because it halts the cell cycle in response to DNA damage thus allowing time for repair

Question 19

What are some genes that p53 regulates?

Answer 19

p21: mitotic arrest
GADD45: DNA repair protein

Question 20

What happens when p53 becomes mutated?

Answer 20

Converts from a tumor suppressor to an oncogene.

Associated with ~50% of all tumors when mutated

Question 21

When is p53 activated/phosphorylated?

Answer 21

In response to DNA damage

Question 22

When is pRb inactivated/phosphorylated?

Answer 22

In response to cdk2 resulting in released E2F that can bind DNA and regulate expression of cell division genes

Question 23

What happens in M phase following G2?

Answer 23

Prophase
Prometaphase
Metaphase
Anaphase
Telophase

Question 24

What happens in prophase?

Answer 24

Chromosomes condense; nucleoli disappear, mitotic spindle forms

Question 25

What happens in prometaphase?

Answer 25

Nuclear membrane breaks down; chromosomes attach to spindle

Question 26

What happens in metaphase?

Answer 26

Chromosomes maximally contracted and arranged at equatorial plane

Question 27

What happens in anaphase?

Answer 27

Centromeres split and sister chromatids separate to opposite poles

Question 28

What happens in telophase?

Answer 28

Chromosomes decondense, nuclear membrane reforms, cytokinesis

Question 29

What is required in metaphase to anaphase transition?

Answer 29

M-Cdk inactivation required.

Question 30

What is required from prophase to metaphase?

Answer 30

Active m-Cdk

Question 31

What are the targets of M-Cdk?

Answer 31

Condensins | Laminin

Question 32

What are Condensins?

Answer 32

Proteins involved in chromosome condensation

Question 33

What does phosphorylation of laminin cause?

Answer 33

Causes it to depolymerize, resulting in nuclear envelope breakdown

Question 34

What does APC affect?

Answer 34

Securin Separase Cohesins

Question 35

What is securin and what is one of its functions?

Answer 35

Separase inhibitor It initiates anaphase (APC target)

Question 36

What is separase?

Answer 36

A protease that targets cohesion to allow sister chromatid separation

Question 37

What is involved in programmed cell death?

Answer 37

Removal of factors Extracellular signals Cell damage

Question 38

What are oncogenes?

Answer 38

Mutated forms of normal proteins (proto-oncogenes) involved in control of cell growth

Question 39

How can viruses become tumor causing?

Answer 39

1) virus inserts into host genome 2) when excised May take a cope of genome with it 3) mutates the genome 4) reinfect and inserts mutated gene into new host

Question 40

What are some known oncogenes?

Answer 40

Mutant G proteins and tyr-kinases?

Question 41

What does erbB encode?

Answer 41

EGF receptor lacking EGF binding domain

Question 42

What does sis encode?

Answer 42

Mutant PDGF receptor

Question 43

What does ras encode?

Answer 43

A G protein with no intrinsic GTPase activity

Question 44

What does myc encode?

Answer 44

A transcription factor that regulates proliferative proteins

Question 45

What is different about the ErbB protein?

Answer 45

Tyrosine kinase is constantly active

Question 46

What is HPV highly associated with?

Answer 46

Cervical cancer

Question 47

What do the early HPV proteins (E6 & E7) do?

Answer 47

They bind and inactivate p53 and pRb the tumor suppressing proteins

Question 48

What else does HPV E6 do?

Answer 48

Targets Bcl2 which helps maintain a cell that should undergo apoptosis