AP BIOLOGY

Detailed explanation-1: -Prophase is the first stage of mitosis. In prophase, chromosomes condense and become visible. spindle fibers emerge from the centrosomes.

Detailed explanation-2: -Spindle Fiber Formation The spindle fibers begin to form during prophase of cell division. The cell’s centrosomes-small organelles that organize and arrange the microtubules-begin to form microtubules.

Detailed explanation-3: -During prometaphase the microtubules of the mitotic spindle attach to the kinetochores of condensed chromosomes. The kinetochores of sister chromatids are oriented on opposite sides of the chromosome, so they attach to microtubules emanating from opposite poles of the spindle.

Detailed explanation-4: -More specifically, in the first part of anaphase-sometimes called anaphase A-the kinetochore microtubules shorten and draw the chromosomes toward the spindle poles.

Detailed explanation-5: -In contrast to anaphase A, where the depolymerization of kinetochore microtubules is coupled to chromosome movement toward the poles, in anaphase B, the overlap microtubules actually elongate, helping to push the spindle poles apart. Anaphase B is driven by two distinct forces (see Figure 18-26).