Answer:
Sister chromatids:
The chromatids of replicated chromosome that are joined through a centromere is known as sister chromatids. These chromatids are identical to each other. They contains the same allele at similar loci. They are formed at the synthesis phase of cell cycle.
Non-sister chromatids:
The chromatids of the different homologous chromosomes are known as non-sister chromatids. These chromatids are non- identical to each other. They contains the different allele at similar loci. They are formed at the prophase I of phase of meiosis.