A chromatid forms one part of a chromosome after it has coalesced for the process of mitosis or meiosis. Each chromosome consists of two exactly identical ("sister") chromatids. After they have been pulled apart by the mitotic spindle, chromatids are called "chromosomes". Sister chromatids are joined at a point called the centromere. In non-gametic, non-dividing human cells, there are 23 pairs of chromosomes, thus 46 chromosomes. When it is ready to divide, each chromosome will replicate itself during the Synthesis phase within its life cycle. Chromosomes that have replicated stay together, held by the previously mentioned centromere. Because one chromosome became two, the two copies are now called sister chromatids, or generally, chromatids.