Chromosome:1. Chromosomes are single physical structure and hereditary traits, which are transmitted through them.2. The structure of chromosome is best studied at the metaphase, which possesses two chromatids held by a single centromere.Chromatid:1. Each chromosome consists of two symmetrical strands called chromatids, formed during S-phase.2. Each chromatid is half of the metaphase chromosome. Anaphase chromosomes have only one chromatid, due to the splitting of centromere, which becomes the chromosome.