Ribonucleic acid (RNA) is a polymer of ribonucleotides composed of ribose sugar and nitrogen bases Adenine (A) Guanine (G), Cytosine (C) and Uracil (U) which are joined together by a phosphodiester bond.
Occurrence: RNA is synthesized in in nucleus but it is found in nucleolus, mitochondria, chloroplast, nissil granules and cytoplasm and on the membranes of ribosomes. RNA also acts as a material for some viruses.
Structure of RNA
Types of RNA
On the basis of presence of genetic mechanism RNA are of two types:
It acts as a genetic material and is found in most of the the plant viruses some animal viruses and certain bacteriophages. Genetic RNA is found in the absence of DNA and has self-replication property.
Non genetic RNA
Non genetic RNA is found in all organisms except some viruses and occurs in association with DNA. Such RNA has no role in hereditary mechanism but it helps in biosynthesis of proteins hence are non genetic.
On the basis of molecular size and functions they are three major types of non genetic RNA they are
Ribosomal RNA (r- RNA)
Messenger RNA (m-RNA)
Transfer (t- RNA)
Functions of RNA
Differences between DNA and RNA
|Deoxyribonucleic acid (DNA)||Ribonucleic acid (RNA)|
|It is double stranded and coiled||It is single stranded and non helical|
|It consists of deoxyribose sugar||It consists of ribose sugar|
|Purine bases are Adenine (A)and Guanine (G) whereas Pyrimidine bases are Cytosine (C) and Thymine (T)|
Purine bases are Adenine(A), Guanine(G)
Pyrimidine bases are Cytosine (C) and Uracil (U)
|It has equal proportions of purines and pyrimidines||Purines and Pyrimidines are not equal in proportion.|
|It is hereditary material of all organisms.||It is not hereditary material except for some viruses.|
|It carries genetic information from generation to generation.||It participates in protein synthesis|
|DNA can form RNA by the process of transcription.||RNA cannot give rise to DNA under normal conditions.|