When prophase is complete, the cell enters prometaphase — the second stage of mitosis. During prometaphase, phosphorylation of nuclear lamins by M-CDK causes the nuclear membrane to break down into numerous small vesicles. As a result, the spindle microtubules now have direct access to the genetic material of the cell.
Each microtubule is highly dynamic, growing outward from the centrosome and collapsing backward as it tries to locate a chromosome. Eventually, the microtubules find their targets and connect to each chromosome at its kinetochore, a complex of proteins positioned at the centromere. The actual number of microtubules that attach to a kinetochore varies between species, but at least one microtubule from each pole attaches to the kinetochore of each chromosome. A tug-of-war then ensues as the chromosomes move back and forth toward the two poles.
Cells duplicate and condense their DNA prior to entering mitosis. ... Early microscopists were the first to observe these structures, and they also noted the ... forms of chromosomes leading up to and during cytokinesis, the ultimate division of one ... condensin forms rings that coil the chromosomes into highly compact forms.
The less moveable end of the skeletal muscle is the medial or proximal end. It can be found near the point of attachement of the bones called as origin. It can be observed near the midline of the body.
