 Let us see different types of RNAs. As you know, only one type of DNA is present in the cells, but the ribonucleic acids, they are of three types, present in the living organisms. And these are messenger RNA or generally called as mRNA, transfer RNA or TRNA and ribosomal RNA or RRNA. So these three types of ribonucleic acids are present in the cells of living organisms. First type is the messenger RNA. As you know, the process of protein synthesis is carried out in the cytoplasm and you also know the DNA is only present in the nucleus. It does not go out to the cytoplasm. So how it conveys message from nucleus to the site of protein synthesis in the cytoplasm to synthesis the protein. So definitely there will be some messenger and this messenger is a ribonucleic acid and this messenger is mRNA or messenger RNA. It is that type of RNA that carries genetic information from DNA to the protein biosynthetic machinery that is ribosomes, which is present in the cytoplasm. This mRNA provides the templates that specify amino acid sequences in the polypeptide chain because this mRNA molecule, it takes the information from DNA. So it contains the templates copied from DNA and these templates are then translated in the form of sequence of amino acids in a protein molecule. So this mRNA is synthesized in the nucleus from DNA and then after synthesis it is transported from nucleus to the cytoplasm. The process of synthesis of mRNA on a DNA template in the nucleus is known as transcription. This mRNA molecule as you know it is for the synthesis of a particular protein and the synthesis of a protein is specified by a particular gene. So actually this mRNA molecule contains information of a particular gene. It may contain the information of one gene or more than one gene. So it may be monocystronic or polycystronic. In case of monocystronic this mRNA molecule it is only called one gene. That is it is responsible for the synthesis of only one type of protein. While in case of a polycystronic mRNA it contains the information for more than one gene. So it is responsible for the synthesis of more than one type of the proteins. So the length of mRNA molecule it is variable because it may be monocystronic containing one gene or it may contain many genes and then the length of gene is also very variable. So the length of mRNA molecule is also variable. The second type of ribonucleotide which is present in the cytoplasm that is transfer RNA or tRNA. Transfer RNA serves as an adapter molecule in the process of protein synthesis. How it acts as adapter? To one end this tRNA molecule is linked with an amino acid. So it carries that amino acid to the site of protein synthesis that is to the ribosome. So in this way it is acting as an adapter. So the main function of transfer RNA as the name is indicating is the transfer of amino acid from different sites of the cytoplasm to the site of protein synthesis in the cytoplasm. These transfer RNA molecules they pair with mRNA in such a way that the amino acids which are carried by these tRNA molecules they are joined to the growing polypeptide chain in a correct sequence. So as you can see in this illustration this is tRNA molecule and it contains an amino acid which is covalently attached with this tRNA molecule and here you can see a specific sequence of three letters. This sequence is called anticodon and this anticodon is complementary with the sequence of three letters on mRNA. So this tRNA molecule will combine with the mRNA with the help of this specific anticodon and when this tRNA molecule attaches here with this protein synthetic machinery it hands over its amino acid to the already growing polypeptide chain and after handing over its amino acid it goes out of the synthetic complex and here you can see this tRNA molecule is without any amino acid. So in this way new tRNAs with new amino acids come they give their amino acid to the polypeptide chain and they go out without the amino acid. In this way they help in the synthesis of proteins. The third type of ribonucleic acid is ribosomal RNA or RRNA. Ribosomal RNAs are components of the ribosomes and ribosomes are the protein synthetic machineries. Ribosomal RNA is a predominant material in the ribosome and it comprises about 60% of ribosomes by weight. It has a number of functions to perform in the ribosome during the process of protein synthesis.