14. The genetics of the cell cycle

Question 1

how do yeast cells divide

Answer 1

budding

Question 2

what is the first control point called in yeast called

Answer 2

START

Question 3

who won the Nobel prize for identifying genes involved in the cell division

Answer 3

Lee Hartwell

Question 4

describe temperature sensitive mutant studies

Answer 4

temp. sensitive mutants could grow at temps up to 25 deg.C

addition of a functional copy of the gene rescues the mutant when temperature is too high

Question 5

what process was used to test the temp. sensitive mutants

Answer 5

complementation

Question 6

how were functional genes added to the mutants

Answer 6

wild-type yeast genome is digested and ligated into plasmids

Question 7

what gene allows survival of cells at higher temperatures

Answer 7

cdc28

Question 8

what is cdc28 a component of

Answer 8

S-phase promoting factor

a CDK

Question 9

at high temperatures. what happens to temp-sensitive mutants, in regards to cyclin

Answer 9

it dissociates = no growth - cannot move from the G1 to S phase

Question 10

what do cdc28 mutant cells transformed with G1 cyclin plasmids show

Answer 10

functional complex

= progression through mitosis

Question 11

in S. pombe, what does the size of the cell show

Answer 11

shows what phase the cell is in - it is intrinsically linked

Question 12

what is complementation

Answer 12

experiments that use mutants to see whether the addition of certain genes can recover cell growth in specific conditions

Question 13

what causes the arrest of S. pombe during fission, at what stage

Answer 13

cdc mutants

G2/M arrest

Question 14

what is the difference between budding and fission in yeast in terms of control point

Answer 14

budding= major control point G1/S phase

fission = major control point G2/M phase

Question 15

what is the difference between budding and fission in yeast in terms of cell size

Answer 15

budding = produces a bud

fission = intrinsically linked to cell length, the longer the cell the further through fission it is

Question 16

give an example of a yeast that does fission

Answer 16

schizosaccaromyces pombe

Question 17

give an example of a yeast that does budding

Answer 17

saccharomyces cerevisiae

Question 18

cdc28 is another term for what

Answer 18

CDK1

Question 19

what is the structure of CDK s in eukaryotes

Answer 19

highly conserved

Question 20

S. pombe ts mutants can also be rescued by cdc28, and what else?

what does this show?

Answer 20

human CDK1

structurally and functionally conserved in eukaryotes

Question 21

what happens to cdc2 knockout cells

Answer 21

they continue to grow, but are unable to enter mitosis

CANNOT MOVE FROM G2 INTO S PHASE

Question 22

what 2 genes activate MPF

Answer 22

Wee1

Cdc25

Question 23

what regulates CDK activity

Answer 23

cyclin binding

phosphorylation

Question 24

what is Wee1

Answer 24

a kinase

Question 25

what is Cdc25

Answer 25

a phosphatase

Question 26

when does cyclin expression occur

Answer 26

late S/G2 phase

Question 27

what is required to activate Cdc2

Answer 27

phosphorylation at T161 by CAK

Question 28

what does CAK stand for

Answer 28

CDK activating kinase

Question 29

for full activity of MPF, what else must happen to Cdc2

Answer 29

dephosphorylation of tyrosine 15 by Cdc25

Question 30

how does Wee1 inhibit MPF

Answer 30

by inhibitory phosphorylations of tyrosine 15

Question 31

what happens if there is excess wee1 and deficit of cdc25

Answer 31

large cells = no mitosis

Question 32

what happens if there is deficit of wee1 and excess cdc25

Answer 32

small cells = innapropriate mitosis