Exam 4 Lesson 35

Question 1

What does cell cycle control influence?

Answer 1

Development, tissue regeneration, repair

Question 2

At what part of cell cycle does mitogen kick in?

Answer 2

At G1, which is “start” for yeast or “restriction” for animal cells.

Question 3

What would cells leave cell cycle at G0?

Answer 3

Mature neurons leave. Damaged cells would leave.

Question 4

What parts of cell cycle make up interphase?

Answer 4

G1 and S and G2

Question 5

What is the status of chromatin in interphase?

Answer 5

It is condensed, or heterochromatic.

Question 6

Do all cells divide at same rate?

Answer 6

No. Some cells divide at a faster rate than others.

Question 7

Which part of cell cycle is usually the longest?

Answer 7

G1. It can last hours to years.

Question 8

Early frog embryo cell cycle time

Answer 8

30 minutes

Question 9

Yeast cell cycle time

Answer 9

1.5-3 hours

Question 10

Mammalian intestinal epithelial cells cycle time

Answer 10

~12 hours

Question 11

Mammalian fibroblasts in culture cycle time

Answer 11

~20 hours

Question 12

Human liver cell cycle time

Answer 12

~1 year

Question 13

After cell becomes committed to S, G2, M, how long does all that take?

Answer 13

Less than one day.

Question 14

What model systems do we use to study the cell cycle?(4)

Answer 14

Xenopus laevis, drosophila, mammalian cells, yeast

Question 15

What are the benefits of xenopus laevis as a cell cycle model?

Answer 15

a. controllable in vitro fertilization b. oocytes have high protein and RNA for biochem studies c. eggs can be injected with RNA, chemical inhibitors and more d. egg cytoplasm can be collected d. large cells

Question 16

how is xenopus laevis controllable in vitro fertilization?

Answer 16

It has rapid cell division after 90 minutes and it has synchronous cell division.

Question 17

What is a maturation promotion factor (MPF)?

Answer 17

A diffusible factor from egg induces M-phase in interphase cell. Works in somatic cells too.

Question 18

What is a cell-free system?

Answer 18

Cytoplasm from activated frog egg and nuclei from frog sperm are put into oocyte.

Question 19

Cell-free system cell cycle: how do transcription inhibitors affect cycle?

Answer 19

Transcription inhibitors have no effect on cell cycle.

Question 20

Cell-free system cell cycle: how does treatment of cytoplasm with RNAse affect cell cycle?

Answer 20

M-phase inducing activity is lost

Question 21

Cell-free system cell cycle: how do translation inhibitors stop the cell cycle?

Answer 21

Translation of only one type of mRNA is needed for cycling, so translation inhibitors need to inhibit all translation to stop cell cycle.

Question 22

What is the advantage of the drosophila cell cycle model?

Answer 22

Drosophila experiences synchronous cell divisions. Also, large cells.

Question 23

What is heterokaryon?

Answer 23

Multiple nuclei

Question 24

Rao and Hohnson Nuclear Fusion: what was the purpose of this experiment?

Answer 24

To see what the order of cell cycle stages was. This experiment with mammalian cells helped place events.

Question 25

What are the two types of yeasts?

Answer 25

S. pombe (fission yeast) and S. cereviseae (budding yeast)

Question 26

What is S. cereviseae?

Answer 26

Baker’s yeast

Question 27

What are the advantages of using yeast for cell cycle modeling?

Answer 27

a. small, fast growing b. small, fully sequenced genome c. cell morphology tells phase of cell cycle d. can grow as haploids

Question 28

What is the benefit of using haploids for experiments?

Answer 28

Mutagenesis. It is easier to cause a mutation in genetics in haploids.

Question 29

What are conditional mutants?

Answer 29

Temperature sensitive mutants. At 25 degrees Celsius, no phenotype. At 37 degrees Celsius, there is a phenotype that shows “cell cycle arrest” because it is too warm.

Question 30

What is in situ DNA labeling?

Answer 30

Labeling in tissue

Question 31

What is Brdu?

Answer 31

Analog of thymidine

Question 32

What is the problem with using cultured cells (animals, plants, yeasts)?

Answer 32

They grow asynchronously. They will end up at different phases of cell cycle.

Question 33

How do you study asynchronous cells?

Answer 33

a. induce synchrony b. isolate cells of specific size, shape and DNA content

Question 34

how does one induce synchrony?

Answer 34

Add inhibitors for a. DNA synthesis cells accumulate in S-phaste and b. microtubule formation cells accumulate in M phase (mitotic spindles)

Question 35

One can also remove mitogens to induce synchrony. What happens if mitogen is removed?

Answer 35

FBS (fetal bovine serum). Cells accumulate at restriction/start when mitogen is removed.

Question 36

What is the benefit of isolating cells based on size, shape, DNA and protein content?

Answer 36

Cells differ in shape and size at all different stages of cell cycle. Rounded up cells are smallish. Late G2 cells are very large, for example.