Lecture 21

Question 1

What phase do mitotic cyclins begin to increase?

Answer 1

S-phase

Question 2

When do mitotic CDKs increase in concentration?

Answer 2

almost at the end of G2

Question 3

How are mitotic CDKs bound with mitotic cyclin held inactive?

Answer 3

Tyr and Thr residues are phosphorylated on CDK-inhibitor site

Question 4

What activates the mitotic cyclin-CDK complex?

Answer 4

Cdc25 phosphatase

Question 5

Function of mitotic CDKs

Answer 5

ensures that the spindle formation and attachment of chromosome is correct

Question 6

What is amphitelic MT attachment

Answer 6

stable attachment with use of mitotic CDKs

Question 7

what is merotelic MT attachment

Answer 7

one MT on one side and three on the other side

Question 8

what makes merotelic MT attachment unstable?

Answer 8

aurora B phosphorylates with each other = loose unstable attachment

Question 9

what is syntelic MT attachment

Answer 9

MTs from only one side attach to both sides of kinetchores

Question 10

what is monotelic MT attachment

Answer 10

MTs only attach to one side of kinetochores

Question 11

In the cell cycle, when do we want to remove the centromere cohesins?

Answer 11

before anaphase happens

Question 12

What checkpoint in the cell cycle checks for amphitelic MT attachment and correct orientation of MT spindles??

Answer 12

spindle checkpoint

Question 13

What is securin?

Answer 13

a protein that inactivates separase

Question 14

What is the function of separase?

Answer 14

cleaves off cohesins of chromosomes

Question 15

How is separase activated?

Answer 15

APC/C ubiquitinylates securin for degradation = activates separase

Question 16

What is Cdc14?

Answer 16

a protein phosphatase

Question 17

What is beneficial about Cdc14 with Sic1?

Answer 17

it keeps Sic1 unphosphorylated to prevent DNA replication from happening before S-phase

Question 18

When is APC/C the most active?

Answer 18

right after mitosis

Question 19

What phosphorylates Cdh1 of APC/C to inactivate it? Why?

Answer 19

G1/S-phase CDKs to prevent degradation of G1/S-phase cyclins and CDKs

Question 20

What is Sic1 attached to and what needs to be done in order to move onto DNA replication?

Answer 20

phosphorylate Sic1 which is attached to the S-phase cyclins/CDKs and inactivates it

Question 21

What holds the mitotic cyclin/CDK complex inactive prior to mitosis?

Answer 21

Wee1 kinase

Question 22

What phosphorylates Cdh1 to activate APC/C?

Answer 22

Cdc14

Question 23

If the cell’s surveillance mechanisms (cell cycle checkpoints) detect DNA damage, what happens?

Answer 23

pauses cell cycle and allows DNA to repair while preventing the start of mitosis

Question 24

What are the three options that a cell can take once DNA damage has been detected and the phosphorylated kinases are ready to fix the problem?

Answer 24

DNA repair, prevent Cdc25 functions, or activate p53

Question 25

Which cycle does the cell initially check for DNA damage? What, then, happens?

Answer 25

G1, p21 prevents the expression of G1 CDKs = pauses cell cycle

Question 26

If DNA damage is detected in S-phase, what happens?

Answer 26

cell cycle prevents G1/S-phase CDKs from activating DNA synthesis

Question 27

If replication stress is detected in S-phase, what happens?

Answer 27

S-phase CDKs are inactivated = pauses cell cycle

Question 28

If DNA replication happened late, what happens?

Answer 28

cell cycle is stopped to ensure that DNA replication is completely done prior to mitosis

Question 29

what does the spindle assembly checkpoint checks for?

Answer 29

correct chromosome attachment to spindles prior to segregation, chromosomes must be under tension

Question 30

What happens if the kinetochore complex are not attached to MT?

Answer 30

kinetochore complex will be phosphorylated = leads Mitotic Checkpoint Complex (MCC) to associate with APC/C to inactivate it = pause cell cycle to allow MT attachment

Question 31

What does the Spindle Position Checkpoint pathway check for?

Answer 31

nucleus is accurately partitioned between two daughter cells, spindles must be positioned correctly

Question 32

What is different about meiosis compared to mitosis?

Answer 32

only happens in gametes, homologous chromosomes, daughter cells are not genetically identical, reduction division and crossing over happens

Question 33

What is meiosis I also called?

Answer 33

reduction division (cells still 2n)

Question 34

What is meiosis II equivalent to?

Answer 34

mitosis when 2n --> n

Question 35

What is Rec8?

Answer 35

cohesin used in meiosis between sister chromatids

Question 36

When does Rec8 get cleaved off?

Answer 36

Metaphase II