Anaphase is a stage in cell division which occur in mitosis (the process of cell division in somatic cells, those which carry out the many functions within the body but which are not concerned with a reduction in the number of chromosome prior to sexual reproduction) and meiosis where the genetic material is halved prior to fusion between male and female gametes. Anapahase is over in a a matter of minutes.
In mitosis each pair of chromatids separate into 'daughter chromatids' - each set will will go into each of the two cells that result from the cell division. In meiosis the chromosomes (each chromosome consists of two chromatids) part company at anaphase I (left diagram) and move to opposite end of the cell so that during telophase one set is extruded as a polar body. In anaphase II (right diagram) the chromatids part company any move to opposite ends of the cell in response to the penetration of the sperm during fertilisation.
Mistakes during anaphase I and Anaphase II in meiosis may lead to daughter cells having the wrong complement of chromosomes - referred to as non-disjunction - Down's syndrome, for example has 47 rather than 46 chromosomes with the cell often trying to eliminate the extra set of chromosomes. See also aneuploidy.