Question

What is the meaning of deoxyribonucleic acid. What is it?

Answer 1

There are two types of nucleic acid, Deoxyribonucleic acid ( DNA) and ribonucleic acid (RNA). They act as the genetic material in organisms. The former is the genetic material in the majority of organisms whereas the latter acts as genetic material in a few viruses.

Complete answer: DNA is the deoxyribonucleic acid which is the genetic material in the majority of organisms that means it carries the character from one generation to the next generation (from parents to offspring).
It is the long polymer of deoxyribonucleotides. Nucleotides consist of 3 components – pentose Sugar (Deoxyribose), Nitrogenous base (purine and pyrimidine), and Phosphate group.
There are two types of nitrogenous bases. Purine and pyrimidine. Purine consists of Adenine, Guanine, and Pyrimidine consisting of Cytosine, Uracil, and Thymine(in DNA thymine is present in place of uracil and vice-versa in RNA).
Due to the presence of phosphate group DNA is acidic in nature and has a negative charge overall. It was first identified by Friedrich meischer and he gave the name ‘Nuclein’ to it.
DNA is present in a double helix form and its double helix model was proposed by James Watson and Francis crick with the help of the X-ray crystallography method developed by Wilkins and Franklin.
And the main principle of their model is the base pairing and this proposition was proposed by Chargaff. According to the chargaff, complementarity exists between the nitrogenous bases like Adenine pairs with Thymine (or uracil in case of RNA), guanine pairs with Cytosine.
Also the ratio of Adenine and thymine, and, Guanine and Cytosine are constant and is equal to one.
Features of Double helix Structure of DNA:

1. double helix structure consists of two polynucleotide chains which run anti-parallel to each other and its backbone is constituted by Sugar- phosphate while nitrogenous base projects inside.
2. Nitrogenous bases are paired with the H-bond between them. Adenine binds with thymine with 2 hydrogen bonds while there are 3 hydrogen bonds between Cytosine and Guanine.
3. This helix is coiled in the right-handed fashion and the pitch of the helix is 3.4nm and there are about 10 base pairs in each turn.

Additional information:
Central dogma theory was proposed by the crick. According to it, genetic information flows like this, DNA to RNA and RNA to protein.

Note: RNA acts as both genetic material (in viruses) and enzyme (called ribozyme). It has many roles as it acts as a messenger RNA, it has a catalytic role (rRNA ), and acts as an adapter (t-RNA).