During anaphase II of meiosis, sister chromatids separate and move to opposite poles of the cell. At this point each separated chromatid is counted as its own chromosome, so the number of chromosomes present depends on the species being discussed.
Using humans as the standard example: a cell entering meiosis II (after meiosis I has already reduced the chromosome number by half) contains 23 chromosomes, each made up of two sister chromatids (46 total chromatids). During anaphase II, the centromeres split and the sister chromatids pull apart, becoming individual chromosomes. Each resulting daughter cell then ends up with 23 chromosomes once division completes — but during the anaphase II stage itself, before cytokinesis, the single cell transiently contains a total of 46 individual chromosomes (23 moving toward each pole).
The key concept to remember is the distinction between chromosome number and chromatid number:
- Before anaphase II (in prophase II/metaphase II), there are 23 chromosomes, each with 2 chromatids (46 chromatids total).
- After the centromeres split in anaphase II, there are 46 individual chromosomes (23 at each pole), each now a single chromatid.
For any other organism, apply the same logic: take the haploid chromosome number (n) that entered meiosis II, and during anaphase II the total chromosome count in the cell doubles to 2n individual chromosomes because sister chromatids separate and are recounted as distinct chromosomes, before the cell divides into two haploid daughter cells with n chromosomes each.
This is a normal and expected part of meiosis, ensuring that after both meiotic divisions, gametes end up with half the chromosome number of the original parent cell.