Question

19. What is the function and structure of DNA?

Answer 1

Structure of DNA

DNA is known as Deoxyribonucleic acid, the molecule of DNA are polymers and it contains monomers that makes it, there are following parts of DNA

1. Four nucleotide monomers bases (base pairs)- the DNA has four nucleotide monomers bases. Abbreviated as A, C, T, and G. Each nucleotide monomer is built from three simple molecular parts: a sugar, a phosphate group, and a nucleobase. A stands for adenine, C stands for cytosine, T stands for thymine and G stands for Guanine.
2. Sugar backbone - The sugar and acid in all four monomers are the same, all four nucleotides (A, T, G and C) are made up by sticking a phosphate group (The phosphate group is a phosphorous atom with four oxygen atoms bonded to It.) and a nucleobase to a sugar. The sugar in all four nucleotides is known as deoxyribose. It’s a cyclical molecule, most of its atoms are arranged in a ring-structure. The ring contains one oxygen and four carbons. A fifth carbon atom is attached to the fourth carbon of the ring. Deoxyribose also contains a hydroxyl group (-OH) attached to the third carbon in the ring.
3. Phosphodiester bonds - the nucleotide monomers in a DNA polymer are connected by strong electromagnetic attractions called phosphodiester bonds.

Double helix structure of DNA - Chromosomal DNA consists of two DNA polymers that make up a 3D structure known as a double helix. In a double helix structure, the strands of DNA run antiparallel, meaning the 5’ end of one DNA strand is parallel with the 3’ end of the other DNA strand. The nucleotides forming each DNA strand are connected by hydrogen bonds, though hydrogen bonds are weaker than other bonds but because there are so many of them, nucleotides are bind together very tightly to each other and hold the structure steady. Adenine (“A”) and Thymine (“T”) each have one donor and one acceptor thus forming two hydrogen bonds between them, whereas Cytosine (“C”) has one donor and two acceptors, and Guanine (“G”) has one acceptor and two donors. Thus forming triple hydrogen bond between them. Adenine always bind with Thymine and cytosine always bind with guanine.

The major groove occurs where the backbones are far apart, the minor groove occurs where backbones are close together.

Functions of DNA

1. DNA polymers direct the production proteins by transcription to mRNA and ultimately translating the sequence into amino acids.
2. DNA contains the genetic information of the organism so it governs the passage of genetic information from parents to offspring.
3. Mutation – whenever required the gene may undergo mutation to alter the characteristic of the organism.
4. Gene expression – gene expression controls how the particular cell will behave and what it would produce for the survival of the organism.