Ribosomal RNA (rRNA)-

The ribosomes are the factories of protein synthesis. The eukaryotic ribosomes are composed of two major nucleoprotein complexes- 60S subunit and 40S subunit. The 60S subunit contains around 35 different proteins and possesses three different rRNA namely; 28S rRNA (4700 bases long), 5S rRNA (12 base long) and 5.8S rRNA (160 base long) while the 40S subunit contain 50 proteins and possesses only one type of rRNA i.e. 18S rRNA, which is about 1900 bases long.

5S r-RNA has a separate gene which is transcribed to form the RNA, whereas, all other RNA are synthesized as a single transcript, which after formation is cleaved to form other RNA molecules. The function of rRNAs in ribosomes is not clearly known. It is believed that they play a significant role in the binding of mRNA to ribosomes and protein synthesis.

However, beside this r-RNA can also act as enzymes. Such RNA molecules are known as ribozymes. The main known role of ribozymes is in the process of splicing of introns. In eukaryotes formation of r-RNA occurs from a small region of DNA. Ribosomal RNA is a single strand which might be twisted up in some regions. Prokaryotic ribosomes are also made up of two subunits 30S and 50S. 30S subunit has 16S r-RNA and 50S subunit contains 23S and 5S rRNA. In different types of r-RNA mentioned ―S‖ stands for sedimentation coefficient.