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 [...]
The following points highlight the four main stages involved in synthesis of RNA. The stages are: 1. Binding of RNA Polymerase to DNA 2. Initiation of Transcription 3. Elongation of RNA chain 4. Termination of Transcription. Stage # 1. Binding of RNA polymerase to DNA: RNA polymerase binds to the "promoter site" on the DNA molecule. The promoter site is [...]
The following points highlight the two main adaptational forms of chromosomes. The forms are: 1. Polytene Giant Chromosomes 2. Lampbrush Chromosomes. Form # 1. Polytene Giant Chromosomes: Polytene giant chromosomes are normal interphase chromosomes where homologues become paired and undergo several replications; all the copies so produced remain associated together. Polytene giant chromosomes are typically found in salivary gland cells [...]