what is the major constituent of a chromosome
Centromere The centromere is the specialized DNA sequence of a chromosome that links a pair of sister chromatids (a dyad).[1] During mitosis, spindle fibers attach to the centromere via the kinetochore.[2] Centromeres were first thought to be genetic loci that direct the behavior of chromosomes.
Sister chromatids Compare sister chromatids to homologous chromosomes, which are the two different copies of a chromosome that diploid organisms (like humans) inherit, one from each parent. Sister chromatids are by and large identical (since they carry the same alleles, also called variants or versions, of genes) because they derive from one original chromosome. An exception is towards the end of meiosis, after crossing over has occurred, because sections of each sister chromatid may have been exchanged with corresponding sections of the homologous chromatids with which they are paired during meiosis. Homologous chromosomes might or might not be the same as each other because they derive from different parents.