Exam 4 Part 1

Question 1

interphase

Answer 1

includes G1, S, G2 phases. Cell increases in size, DNA is replicated, and centrosome duplicated

Question 2

prophase

Answer 2

duplicated chromosomes (each consisting of two closely associated sister chromatids), condense. The mitotic spindle assembles between the two centrosomes, which have begun to move apart.

Question 3

prometaphase

Answer 3

breakdown of the nuclear envelope. Chromosomes can now attach to spindle microtubules via their kinetochores and undergo active movement

Question 4

metaphase

Answer 4

chromosomes are aligned at the equator of the spindle, midway between the spindle poles. The kinetochore microtubules on each sister chromatid attach to opposite poles of the spindle

Question 5

anaphase

Answer 5

sister chromatids synchronously separate and are pulled slowly toward the spindle pole to whichthey are attached. The kinetochore microtubules get shorter, and the spindle poles also move apart, both contributing to chromosome segreation

Question 6

telophase

Answer 6

two sets of chromosomes arrive at the spindle poles. A new nuclear envelope reassembles around each set, completing the formation of two nuclei and marking the end of mitosis. The division of the cytoplasm begins with the assembly of the contractile ring

Question 7

cytokinesis

Answer 7

cytoplasm is divided in two by a contractile ring of actin and myosin filaments, which pinches the cell into two daughters, each with one nucleus

Question 8

quiescent

Answer 8

just living and functioning - when a cell is in G0 phase

Question 9

G1

Answer 9

growing in size, increasing materials

Question 10

S phase

Answer 10

synthesis phase - when DNA is replicated

Question 11

G2

Answer 11

more growth, checking the cell before entering mitosis

Question 12

what the cell cycle must accomplish

Answer 12

events associated with each phase must be performed in the correct time and sequence
must respond to extracellular and intracellular cues
each phase must be completed before the next begins

Question 13

three major checkpoints

Answer 13

G1 - is environment favorable? is DNA damage free? (committed step)
G2 - DNA replicated? Damage reparied? Enough materials?
M- Are all chromosomes attached to spindle? Enough materials present?

Question 14

How to study cell cycle genes when knocking them out disrupts cycle?

Answer 14

Can make temp sensitive mutants or an induced knockout (found a kinase involved)
can also examine the proteins and ID cell cycle promoting factors (xenopus eggs)

Question 15

2 proteins important for mitosis

Answer 15

Cyclin dependant kinases (Cdk)

Cylins

Question 16

cyclins

Answer 16

control the phosphorylation of Cdks
cyclin binding activates Cdk
concentration is cyclic

Question 17

cdk

Answer 17

cyclin dependant kinases

concentration stable throughout cycle, inactive without a cyclin

Question 18

Regulation of cdk

Answer 18

degradation of cyclin
phosphorylation
inhibitor

Question 19

regulation of cdk by degradation of cyclin

Answer 19

ubiquitin binds to cyclin which is a tag to take it to the lysosome
without cyclin, cdk is not active
degradation allows for the concentration occilation

Question 20

regulation of cdk by phosphorylation

Answer 20

inhibitory kinase adds a phosphate to an activated cdk which changes its conformation
the phosphorylation is inhibatory (switches off)

Question 21

regulation of cdk by inhibitor

Answer 21

inhibitory protein binds to entire activated cdk complex and inactivates it
ex. p27, p53

Question 22

why so much cdk regulation?

Answer 22

important to regulate number of cells (too much or too little), need to repair DNA damages