Anaphase is the stage where the centromeres divide. The sister chromatids separate, becoming two daughter chromosomes. Daughter chromosomes (each consisting of a centromere and one chromatid) are pulled toward opposite poles of the spindle. This is due to the disassembly of the kinetochore, this pulls the daughter chromosomes to the poles and the polar spindle fibers lengthen as they slide past one another.
During the final phase, telophase, a nuclear envelope forms around each set of chromosomes, the spindle disappears and the chromosomes decondence. The result is two nuclei, each with the same number and kind of chromosomes as the parental cell.
Meiosis defined: requires two nuclear divisions and produces four haploid daughter cells, each having one kind of chromosome and therefore half the total number of chromosomes present in the diploid parental nucleus. Sexually reproducing organisms are diploid; they have two of every type of chromosome. Prior to sexual reproduction meiosis reduces the number of chromosomes by half and fertilization restores the original number. The divisions are called meiosis 1 and Meiosis 2. Meiosis occurs only at certain times in the life cycle of sexually reproducing organisms. In humans, meiosis occurs only in the reproductive organs and produces the gametes, (egg or sperm).
DNA is replicated prior to the start of meiosis. The identical sister chromatids are joined at the centromere as in mitosis. Unlike mitosis, homologous chromosomes pair with one another. These pairs intertwine during early prophase of the 1st meiotic division and may exchange segments. This exchange is called crossing over.
During prophase 1, the nuclear envelope disappears and the spindle forms. The homologous pairs undergo synapsis. .
Metaphase 1 homologous pairs align as they reach the midplane of the spindle and attach to spindle fibers.
Anaphase 1 begins as the partners in each pair of homologous chromosomes separate as they are pulled to opposite poles by kinetochore spindle fibers.
