Chromosome: Structure and Components
U. K. Laemmli and coworkers put forward the hypothesis of nonhistone proteins scaffold, based on the electron microscopic observations on surface-spread metaphase chromosomes. The continued equational division of zygote subsequent to embryo leads to the development of the adult individual, where all cells theoretically contain the same basic chromosome complement. The process of mitosis and meiosis, that is, equational and reductional division, ensures that every cell of individual contains not only the same number of chromosomes but also all the genes of the complements. In the basic chromosome structure, the chromonema thread is seen to have dense thickened areas with thinner regions in between, giving the appearance of a string of beads. Chromosomes are composed principally of two complexes – heterochromatin and euchromatin. The chromatin responsible for the formation of the nucleolus is its only permanent component. During telophase, the genes located on this segment become active, fibrillar and granular components are synthesized and accumulate in the newly formed nucleolus.