section 8 - part 1 Flashcards
cell cycle has two phases
m phase = mitosis and cytokinesis
interphase = g1 synthesis g2 (gap)
the m phase takes — for a eukaryotic cell to go through mitosis
about a half an hour
interphase takes how long for a eukaryotic cell going through mitosis
hours, days, or weeks
what happens in g1
cell grows and carries out normal metabolism
what happens in the s (dna synthesis) phase
dna is replicated
what happens in the g2 stage
cell grows and prepares for mitosis
is mitosis and these steps able to take error
NO, checkpoints control progression throughout the cell cycle - do not want to mess up mitosis
what is happening in s phase with the chromosomes
start with one chromosome but it duplicates to have each chromosome consist of two sister chromatids that are held together at the centromere
the two sister chromatids separate during…
mitosis
what are the three stages of interphase
g1 - growth and normal metabolism
s - dna synthesis
g2 - growth and prep for mitosis
what properties are involved with interphase
chromosomes, microtubules, and intermediate filaments
key experiment to find features of the cell cycle
- added radioactive thymidine to an asynchronous cell culture
- leave thymidine in culture media for 30 mins - cells incorporate it into DNA that is being replicated (s phase)
- refresh media and wait - do autoradiography to look for labeled DNA
the experiment that helped find the features of the cell cycle is similar to
Pulse-Chase, but with DNA
if cells are not in s phase for this experiment…
the cell will not incorporate it into its DNA, the thymidine will just stay floating around
cells in mitosis are…
not replicating DNA - found by this DNA not being labeled in the experiment bc replication had already happened
s is a — — — of the cell cycle
single short part, only a fraction of the cells were labeled
g2 must be take at least – — between – phase and – phase
there must be a g2 phase of at least 30 minutes between s phase and m phase
- bc there was a gap of 30 mins between the end of the labeling and when the radioactively labeled DNA showed up in compacted chromosomes
phases of mitosis
prophase prometaphase metaphase anaphase telophase
PPMAT
what is MPF
mitosis initiated by protein complex called MPF - maturation promoting factor
what is happening in prophase
- chromosomes start to condense
- centromeres move to opposite poles
- nuclear lamina breaks down
chromosomes condensing in prophase
each chromosome consists of two identical strands (chromatids), joined at the centromere, with terminal regions called telomeres
what are the two proteins important in maintaining compacted mitotic chromosomes in prophase
condensin - organizes DNA to maintain a condensed state, activated by phosphorylation by MPF
cohesin - holds the two sister chromatids together, runs the entire length of chromosomes but lost from the arms in prophase, remains concentrated in the centromere
centromeres are all called — and they –
also called primary constriction
- location of highly repeated DNA sequences
- this DNA is not translated
- repeats are an indication to cell that this is where the kinetochore needs to be assembled
roles of kinetochores, which is –
structure on outer surface of centromere - more than 100 proteins
roles:
1. attachment site between chromosome and microtubules
2. location of some motor proteins that will later be involved in anaphase
3. involved in an important mitotic checkpoint
