#PROTEIN BACKBONE FREE#

All the three RNAs are essential to synthesise a protein in a cell. (iii) rRNA (ribosomal RNA) plays a structural and catalytic role during translation. (ii) tRNA (transfer RNA) carries amino acids and reads the genetic code. Types of RNA (i) mRNA (messenger RNA) acts as the template for transcription. (ii) DNA has evolved from RNA with chemical modifications that makes it more stable because RNA being single stranded and a catalyst, is reactive and hence, unstable. (i) There are some important biochemical reactions in living systems that are catalysed by RNA catalysts and not by protein enzymes. There was evidence to prove that life processes, like metabolism, translation, splicing, etc., have evolved around RNA. RNA RNA (Ribonucleic acid) was the first genetic material. This, in addition to H-bonds, gives stability to the helical structure. The plane of one base pair lies over the other in a double helix.The two strands are coiled in a right-handed pattern.Adenine forms two hydrogen bonds with thymine whereas cytosine forms three hydrogen bonds with guanine. The bases in the two strands are paired through hydrogen bonds between the base pairs.It implies that if one chain has the polarity 5'-3', then the other has 3'-5'. The two DNA chains run antiparallel to each other.Two polynucleotide chains wrap around each other, where the backbone is constituted by pentose sugar and phosphate, and the bases project inside.Structure of DNA The characteristic features of the double helical structure of DNA are as follows: The nitrogenous bases are linked to sugar moieties and project from the sugar-phosphate backbone. The bonding between sugar and phosphate groups forms the backbone of a polynucleotide chain. This is the 3'-end of the polynucleotide chain.

#PROTEIN BACKBONE FREE#

The other end of the polymer has a free 3'-OH (hydroxyl) group of the deoxyribose sugar. A polymer formed in such a manner has a free phosphate group at 5'-end of ribose sugar, which is referred to as 5'-end of polynucleotide chain. Two nucleotides are linked through 3'-5' phosphodiester linkage. A nitrogenous base is linked to the pentose sugar through the N- glycosidic linkage. The negative charge on DNA is due to the presence of the negatively charged phosphate groups. The nitrogenous bases are common in DNA and RNA, except uracil is found in RNA and thymine is present only in DNA. There are two types of purines, namely, adenine and guanine.

Protein backbone