In his article we will discuss about the role of nucleolus in production of ribosomes (explained with diagram). The nucleolus is the site for rRNA transcription and processing as well as for assembly of ribosomal subunits. The nucleolus is organised at the nucleolus organising regions (NORs) of some chromosomes. These chromosomal regions contain the genes for 5.8S, 18S and 28S [...]
In this article we will discuss about the heterochromatin and euchromatin in eukaryotic chromosomes. The terms "heterochromatin" and "euchromatin" were given by Heitz in 1928-29, although they had been discovered much earlier. Heterochromatic blocks observed during interphase were earlier termed as pro-chromosomes. The substance of which eukaryotic chromosomes are composed is known as chromatin; it contains DNA, protein and a [...]
In this article we will discuss about the chemical composition of chromatin. Chromatin is composed of DNA (30-40%), RNA (1-10%) and proteins (50-60%). These constituents vary in different organisms and even in the different tissues of the same species (Table 8.2). Even in the same call, the proportions of DNA, RNA and proteins vary with the stage of cell cycle. [...]