Deoxyribonucleic acid( DNA)

What is Deoxyribonucleic acid (DNA)?

Deoxyribonucleic acid (DNA) is a bio molecule with the characteristics like Self-replicating, mutable, regulate of all biological function and carrier of hereditary information of a living cell.

Source: textbook collection of nobleman.

Pic: DNA Double helix structure

Table of Contents

1. Structural Unit Of DNA.
2. The physical structure of DNA.
3. Characteristics of DNA molecules according to the double helix model provided by Watson-Crick.
4. The chemical structure of DNA.
5. The functions of DNA.

Structural Unit Of DNA.

The structural unit of Deoxyribonucleic acid is the nucleotide. DNA is a molecular organic acid that is the molecular basis of life. The key component of the eukaryotic cell’s chromosome is DNA. Some viruses contain DNA. It is usually thread-like, but it is circular in shape in prokaryotic cells, mitochondria and in chloroplast.

The physical structure of Deoxyribonucleic acid.

J.D. Watson and Francis H.C. Crick proposed the double helix model of DNA molecule formation. This model is universally accepted and recognized as the most modern and accurate model. M.E.H Wilkins proved the DNA double helix model through dye rays. For this, three scientists received the Nobel Prize in 1973.

Characteristics of DNA molecules according to the double helix model provided by Watson-Crick.

1. DNA is two-stranded, like a ladder in a rotating format.
2. The frames on either side of the stairs are made by alternating combinations of sugar and phosphate.
3. Each frame in the middle of the two-sided frame is made with a pair of nitrogenous bases (A = T, G = C).
4. The two bases are joined by hydrogen bonds. So the stairs have phosphate on the outside and nitrogenous base on the inside.
5. The frames on either side of the stairs are opposite to each other. This type of layout is called antiparallel layout.
6. The guanine in one frame binds to the cytosine in the other frame with three hydrogen bonds (G = C). The adenine in one frame is attached to the thymine in the other frame by two hydrogen bonds (A = T).
7. Each rotation of the ladder (actually the double helix) has a distance of 34A` and this distance is made up of 10 mononucleotides. Therefore, the length of each mononucleotide is 3.4A.

The chemical structure of DNA.

The chemical constituents of DNA are:

1. Five-carbon deoxyribase sugar (2nd placement of carbon is called deoxy because of the lack of oxygen),
2. Phosphoric acid
3. Nitrogenous bases (adenine, guanine, cytosine and thymine).

The functions of DNA.

1. Acts as a structural component of chromosome.
2. Acts as the molecular basis of heredity.
3. Contains and controls all the features of an organism.
4. Traits of the organism are passed down from generation to generation
5. All the physiological and biological functions of the organism act as regulators of action.
6. Serves as the basis for the mutation of the organism.
7. It is capable of repairing any part of the DNA and its helix that may be affected.