Exam 4 Lesson 35 Flashcards
What does cell cycle control influence?
Development, tissue regeneration, repair
At what part of cell cycle does mitogen kick in?
At G1, which is “start” for yeast or “restriction” for animal cells.
What would cells leave cell cycle at G0?
Mature neurons leave. Damaged cells would leave.
What parts of cell cycle make up interphase?
G1 and S and G2
What is the status of chromatin in interphase?
It is condensed, or heterochromatic.
Do all cells divide at same rate?
No. Some cells divide at a faster rate than others.
Which part of cell cycle is usually the longest?
G1. It can last hours to years.
Early frog embryo cell cycle time
30 minutes
Yeast cell cycle time
1.5-3 hours
Mammalian intestinal epithelial cells cycle time
~12 hours
Mammalian fibroblasts in culture cycle time
~20 hours
Human liver cell cycle time
~1 year
After cell becomes committed to S, G2, M, how long does all that take?
Less than one day.
What model systems do we use to study the cell cycle?(4)
Xenopus laevis, drosophila, mammalian cells, yeast
What are the benefits of xenopus laevis as a cell cycle model?
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
how is xenopus laevis controllable in vitro fertilization?
It has rapid cell division after 90 minutes and it has synchronous cell division.
What is a maturation promotion factor (MPF)?
A diffusible factor from egg induces M-phase in interphase cell. Works in somatic cells too.
What is a cell-free system?
Cytoplasm from activated frog egg and nuclei from frog sperm are put into oocyte.
Cell-free system cell cycle: how do transcription inhibitors affect cycle?
Transcription inhibitors have no effect on cell cycle.
Cell-free system cell cycle: how does treatment of cytoplasm with RNAse affect cell cycle?
M-phase inducing activity is lost
Cell-free system cell cycle: how do translation inhibitors stop the cell cycle?
Translation of only one type of mRNA is needed for cycling, so translation inhibitors need to inhibit all translation to stop cell cycle.
What is the advantage of the drosophila cell cycle model?
Drosophila experiences synchronous cell divisions. Also, large cells.
What is heterokaryon?
Multiple nuclei
Rao and Hohnson Nuclear Fusion: what was the purpose of this experiment?
To see what the order of cell cycle stages was. This experiment with mammalian cells helped place events.
What are the two types of yeasts?
S. pombe (fission yeast) and S. cereviseae (budding yeast)
What is S. cereviseae?
Baker’s yeast
What are the advantages of using yeast for cell cycle modeling?
a. small, fast growing b. small, fully sequenced genome c. cell morphology tells phase of cell cycle d. can grow as haploids
What is the benefit of using haploids for experiments?
Mutagenesis. It is easier to cause a mutation in genetics in haploids.
What are conditional mutants?
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.
What is in situ DNA labeling?
Labeling in tissue
What is Brdu?
Analog of thymidine
What is the problem with using cultured cells (animals, plants, yeasts)?
They grow asynchronously. They will end up at different phases of cell cycle.
How do you study asynchronous cells?
a. induce synchrony b. isolate cells of specific size, shape and DNA content
how does one induce synchrony?
Add inhibitors for a. DNA synthesis cells accumulate in S-phaste and b. microtubule formation cells accumulate in M phase (mitotic spindles)
One can also remove mitogens to induce synchrony. What happens if mitogen is removed?
FBS (fetal bovine serum). Cells accumulate at restriction/start when mitogen is removed.
What is the benefit of isolating cells based on size, shape, DNA and protein content?
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.
