Name: RNA World
Uploaded: 2019-07-19
Duration: 5 min 49 s
Description: We know our DNA stores information, and the RNA reads it and transmits it. But which one appeared first? Let’s find out how this really works.

Question

Draw a well labelled diagram of DNA double helix.

Accepted Answer

DNA carries genetic information from one generation to another. It is the main hereditary unit in most of the organisms. The new copy of DNA is formed through the process of replication. Watson and Crick in 1953 proposed the secondary structure of DNA in the form of the famous double-helix model for which they shared the Nobel Prize in 1962 along with Wilkins.

According to this model, DNA has a double-stranded structure where two polydeoxyribonucleotide chains are twisted around one another in a double helix. Both the helices are held together through hydrogen bonds formed between the nitrogen bases. The diameter of the DNA molecule is 20 A $°$ (2nm). The length of the DNA in one complete turn is 34A $°$ (3.4nm), which incorporates 10 base pairs. Therefore, the distance between two adjacent base pairs is 3.4 A $°$ .

Both the strands have a sugar-phosphate backbone and are antiparallel to one another. The antiparallel nature is given by the orientation of the deoxyribose sugar which is opposite in both the strands. Therefore, the 5th carbon atom of the sugar molecule, which is exposed at one end of a strand (5' end), faces the 3rd carbon atom of the sugar in the opposite strand (3' end). The strands are also complementary to each other. This nature is based on the purine-pyrimidine links i.e. if one strand is having a purine base (adenine or guanine) another strand must have a pyrimidine counterpart (cytosine or thymine) e.g. A = T and /G = C. In DNA the nucleotides are joined using phosphodiester bonds.

Draw a well labelled diagram of DNA double helix.

Important Questions on Molecular Basis of Inheritance

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