Question

Briefly explain the molecular structure of the chromosomes give a sketch of it.

Answer 1

Molecular structure of Chromosomes:
According to the recent and widely accepted theory of Dupraw (1965, 1970) and Hans Ris (1967) called unistranded theory, each eukaryotic chromosome is composed of a single, greatly elongated and highly folded nucleoprotein fibre of 100A° thick. This nucleoprotein fibre in its turn is composed of a single, linear, double stranded DNA molecule which remains wrapped in equal amounts of histone and non-histone proteins and variable amounts of different kinds of RNA. Dupraw produced a 'folded-6bre model to show the ultrastructure of chromosome. This model shows a highly folded nucleoprotein fibre in a chromosome and also suggests that how the nucleoprotein fibre of a chromosome replicates during cell division and how the nucleoprotein fibre of both chromatids remain held at the centromere by a unreplicated fibre segment to DNA until the anaphase.

Chromosome:

• The  DNA molecule, in the nucleus of each cell is packaged into thread-like structures called chromosomes.
• Each chromosome is made up of DNA tightly coiled many times around proteins called histones that support its structure.