lecture 20

Question 1

What phases make up interphase?

Answer 1

G1, S, & G2

Question 2

What happens in the G1 phase?

Answer 2

Cell growth

Question 3

Some cells will remain in G1 phase for long periods of time or permanently. What is this called and what are 2 examples of cells that do this?

Answer 3

G0; differentiated nerve & muscle cells

Question 4

What occurs in S phase? (3 things)

Answer 4

1. Replication of the genome (DNA synthesis)
2. DNA is copied by DNA polymerase
3. The duplicate chromosomes remain bound together by proteins called cohesins (until M phase)

Question 5

What happens in the G2 phase?

Answer 5

cell growth

Question 6

M phase includes _________ and __________.

Answer 6

mitosis and cytokinesis

Question 7

Mitosis (nuclear division) has 5 phases. What are they, in order?

Answer 7

“PPMAT”

Prophase, prometaphase, metaphase, anaphase, & telophase

Question 8

What occurs in prophase? (3 things)

Answer 8

1. the replicated chromosomes condense
2. centrosomes (which replicated during S phase) start to move to opposite sides of the nucleus and the mitotic spindle begins to assemble outside the nucleus.
3. Centrosomes shoot out microtubules to form the mitotic spindle

Question 9

What occurs in prometaphase? (3 things)

Answer 9

1. nuclear envelope breaks down
2. this allows the spindle microtubules to contact the condensed chromosomes
3. The microtubules bind to kinetochores located at centromeres of sister chromatids

Question 10

What are kinetochores?

Answer 10

protein complexes which assemble on the condensed chromosomes

Question 11

What happens during metaphase?

Answer 11

Mitotic spindle gathers all of the chromosomes to the center of the spindle

Question 12

What occurs in anaphase? (5 things)

Answer 12

1. The two sister chromatids in each replicated chromosome split apart at the same time
2. spindle draws them to opposite poles of the cell
3. anaphase begins abruptly with the release of the linkage that hold the sister chromatids together.
4. Now chromatids are pulled to the spindle pole to which it is attached
5. This segregates the sets of chromosomes to opposite ends of the spindle.

Question 13

Activation of _______________ triggers the separation of sister chromatids.

Answer 13

Anaphase promoting complex (APC)

Question 14

What phosphorylates APC?

Answer 14

M-Cdk

Question 15

After the APC is phosphorylated, what can then bind to it?

Answer 15

Cdc20 (making it active)

Question 16

What does the active APC ubiquinate?

Answer 16

securin

Question 17

What is securin?

Answer 17

an inhibitor of separase

Question 18

What does separase do?

Answer 18

cleaves the cohesins which allows separation

Question 19

What happens in telophase? (3 things)

Answer 19

1. nuclear envelope reassembles around each of the two sets of separated chromosomes to form two nuclei
2. nucleus expands and chromosomes decondense to interphase state
3. assembly of contractile ring necessary for cytokinesis

Question 20

what is cytokinesis?

Answer 20

cytoplasmic division

Question 21

What happens in cytokinesis?

Answer 21

1. Division of the cytoplasm (including all organelles)

* begins in anaphase and is complete by the end of telophase

Question 22

Which enzyme replicates DNA?

Answer 22

DNA polymerase

Question 23

How many chromosomes are copied?

Answer 23

46

Question 24

In what phase do the sister chromatids separate?

Answer 24

anaphase

Question 25

When does cytokinesis begin and end?

Answer 25

It starts in anaphase and ends in telophase.

Question 26

How does APC trigger anaphase?

Answer 26

ubiquitinates securin