week 2 (cell cycle)

Question 1

how do cells know when to divide? x3 conditions

Answer 1

in response to external signals

DNA replication is complete

the cell is large enough to divide into two

Question 2

progression through the cell cycle is controlled by what 2 things?

Answer 2

cyclins, which are proteins that appear and disappear in a cyclical fashion

cyclin-dependent kinases (CDKs), several enzymes that become active & inactive also in cycles

Question 3

define kinase

Answer 3

enzymes that phosphorylate other molecules

Question 4

why do cyclin-dependent kinases have their name?

Answer 4

they are only active when bound to cyclins

Question 5

active CDKs do what? what happens after this?

Answer 5

phosphorylate target proteins

phosphorylated target proteins promote cell division and progression through the stages of the cell cycle

Question 6

there are 3 specific time points that are regulated. when are these?

Answer 6

g1 to s
s to g2
g2 to m

Question 7

what is the purpose of the g1/s cyclin-CDK complex? and what 2 functions carry this out?

Answer 7

prepares the cell for S phase:

promotes the expression of histone proteins needed to package DNA
& expression and activation of DNA polymerase and other enzymes

Question 8

what is the purpose of the S cyclin-CDK complex? x2

Answer 8

initiation of DNA synthesis
& inhibit the activity of DNA synthesis enzymes once replication is over

Question 9

what is the purpose of the M cyclin-CDK complex? x2

Answer 9

the breakdown of the nuclear envelope during prophase
& the formation of the mitotic spindle

Question 10

B cyclin-CDK complex is responsible for what?

Answer 10

prepares cell for mitosis

Question 11

A cyclin-CDK complex is responsible for what? x2

Answer 11

DNA synthesis & prevents multiple instances of replication

Question 12

D and E cyclin-CDK complexes are responsible for what?

Answer 12

prepare the cell for DNA synthesis

Question 13

3 major checkpoints in the cell cycle (what & where they are)

Answer 13

1. DNA damage checkpoint (just before s phase)
2. DNA replication checkpoint (just before m phase)
3. spindle assembly checkpoint (start of m phase)

Question 14

once activated by phosphorylation, p53 does what? what is the purpose of this?

Answer 14

activates the synthesis of proteins that block G1/S Cyclin-CDK complex

arrest of the cell cycle gives time to repair the damage (this is a “DNA damage checkpoint”)

Question 15

define oncogene

Answer 15

cancer-causing gene

Question 16

what makes rous sarcoma virus dangerous?

Answer 16

has a gene that promotes uncontrolled cell division. it encodes an overactive protein kinase that functions as a signal

Question 17

watch a video on p53 at the damaged DNA checkpoint

Answer 17

-

Question 18

define proto-oncogenes

Answer 18

normal genes important in cell division that have the potential to become cancerous if mutated

Question 19

various proteins that performs roles in signalling cascades leading to cell division can be a product of a proto-oncogene. give 4 examples

Answer 19

growth factors
cell surface receptors
g proteins
protein kinases

Question 20

define tumor suppressors

Answer 20

genes that encode proteins whose normal activities inhibit cell division

Question 21

cell division is regulated by 2 main gene types. what are these & their purposes?

Answer 21

proto-oncogenes that promote cell division
& tumor suppression genes that inhibit cell division

Question 22

development of cancer must take multiple failures of regulartory cell division mechanisms. at the following 4 stages, what is allowing for the progression of cancer to the next stage?

normal cells
benign cancer
malignant cancer
metastatic cancer

Answer 22

n: inactivation of first tumor suppressor gene

b: activation of oncogene

ma: inactivation of second tumor suppressor gene

me: inactivation of third tumor suppressor gene
OR
activation of second oncogene

Question 23

for cancer to develop, typically more than 1 instances of what two events must happen?

Answer 23

activation of oncogene

inactivation of tumor suppressor gene