12.2 mitotic spindle Flashcards
when does the mitotic spindle start to form
in the cytoplasm during prophase
whats a mitotic spindle
fibers of microtubules and associated proteins
- when it assembles, the cytoskeleton disassembles
- it polymerizes and depolymerizes
polymerizes
adds more subunits of the protein tubular
depolymerizes
losing subunits
in animal cells where does the microtubules start to assemble
the centrosome
centrosomes
- microtubule organizing center
- sub cellular region containing materials that function throughout the cell cycle to organize a cell’s microtubules
- they also have 2 centrioles
centrioles
located in center of centrosome but are not important for anything
centrosomes in cycle
interphase) 1 centrosome replicates
pro/prometa) 2 centrosomes move apart and microtubule grow from them
promotaphase) they are at opposite sides with astar extending from each
aster
a radial (diverging) array of short microtubules extending from the centrosomes
the mitotic spindle parts
- the centrosomes,
- microtubules
- aster
kinetochore
proteins on either side of the centromere
-proteins associated with specific sections of chromosomal DNA at the centromere
what happens to the kinetochore in pro metaphase
1) kinetochore microtubules attach to 1 kinetochore and starts to move toward that side
2) kinetochore microtubules attach to the other side and the tug of war
3) ends in a draw at the metaphase plate
4) the rest of the microtubules overlap and interact
kinetochore microtubules
spindle microtubules attach to one kinetochore
the metaphase plate
the plane midway between the spindle’s 2 poles
-imaginary
mitotic spindle in anaphase
both happen depending on cell type
1- motor proteins the kinetochores walk the chromosomes along microtubules and as they pass, the ends depolymerize
2-chromosomes are reeled in by motor proteins at the spindle poles and depolymerize as they pass the motor proteins
