Question

What is a nucleosome? Draw a diagram of the double-stranded polynucleotide chain of DNA and explain its structure.

Answer 1

Hint: DNA is deoxyribonucleic acid. All 23 pairs of chromosomes carry DNA. These are double-stranded coiled helices. These have two polypeptide strands. The model of DNA was given by Watson and Crick. X-Crystallography was used to identify the structure.

Complete answer:
The basic unit of DNA packaging is called nucleosome in eukaryotes. It has eight histone proteins arranged in a sequence.

Structure of double-stranded polynucleotide chain of DNA –
The human genome is a set of nucleic acids sequence in the case of humans which is encoded as DNA with all 23 pairs of chromosomes in cell nuclei. DNA is deoxyribonucleic acid. It is composed of two polynucleotide chains. These coils around each other forming a helix.
It carries information about the genetic development, growth, and functioning of an individual. These also carry the physical trait genes from the parents.
A DNA molecule has a sugar, phosphate, and purine/pyrimidine group.
Major and minor grooves are formed amongst this helical structure. They are formed due to the antiparallel arrangement of base pairs.
Nucleotides are the polymers of subunits in each chain. The deoxyribose sugar is connected to phosphate groups to make the backbone of the DNA.
The 3’ C of sugar molecule is linked to the 5’ C of the phosphate group. This makes the phosphodiester linkage.
The distance between adjacent bases is 3.4 A.
The nitrogenous bases always pair in a fixed pattern that is thymine will pair with adenine and guanine will always pair with cytosine. There are 2 hydrogen bonds between A-T and 3 hydrogen bonds between G-C.

Note: Human genome is a complete set of nucleic acids sequences in humans which is encoded as DNA with all 23 pairs of chromosomes in cell nuclei. DNA is deoxyribonucleic acid. It is composed of two polynucleotide chains. These coils around each other forming a helix. It has a diameter of 2nm. The DNA differs at only 0.1% in the whole genome of the world.