The key difference between sister and nonsister chromatids is that sister chromatids are identical and contain the same allele in the same loci while nonsister chromatids are not identical and contain different alleles of the same gene in the same loci.
The two types of chromatids found in the cell that undergo cell division are sister chromatids and nonsister chromatids. Generally, chromatids form during early stages of cell division. On the other hand, nonsister chromatids form during metaphase I of meiosis. They are present in the homologous chromosome pair on the cell equator while sister chromatids are present in the same chromosome. Moreover, the centromere of the chromosome joins the two sister chromatids together.
