Difference Between mRNA, tRNA & rRNA

Updated July 20, 2017

Environment and experiences play a role in shaping your mind and body, but the structural framework can be traced back to the unique sequence of your genome, or genetic code. The DNA within your cells is strictly confined to the nucleus, the control centre of the cell. A major function of DNA is to instruct the synthesis of proteins, however, this process is actually carried out by the three types of RNA.

Properties of RNA

RNA molecules are all composed of the same four building blocks, known as nucleotides. Information is coded by the arrangement of nucleotides into triplets, known as codons. Each codon corresponds to one of 20 amino acids; this method allows your cells to represent complex, highly variable protein sequence information by ordering these four nucleotides in a specific order.


DNA is the master blueprint upon which all cell processes are based. Within the nucleus, the integrity of your genetic information is protected. However, the process of protein synthesis never occurs inside the nucleus, only within the cytoplasm. To communicate the instructions for this process, your cells use messenger RNA molecules, or mRNA, to relay the information contained within nuclear DNA to the protein synthesising machinery located in the cytoplasm. Thus, genes are translated from DNA into mRNA, which is subsequently transported from the nucleus into the surrounding cytoplasm. The size of mRNA molecules varies considerably, depending on the length of the protein being synthesised.


Transfer RNA is the second type of RNA molecule required for protein synthesis. At this step in the process, the mRNA code is transcribed into a sequence of amino acids. At least 20 different tRNA molecules exist, each corresponding to a unique amino acid. Transfer RNA molecules are able to read the mRNA code and deliver the appropriate amino acid to the growing protein molecule. One unique property of tRNA is its ability to form secondary structures, or complex folding patterns, which enable it to carry out its function.


Also known as ribosomal RNA, this type of RNA serves to stabilise the protein synthesising complex, also known as the ribosome. In humans, ribosomes are made up of two subunits, known as 50S and 30S. These subunits are nucleoproteins and are composed of equal amounts of rRNA and protein. The ribosome will attach itself to the mRNA molecule and stabilise the synthesising protein as amino acids units are attached by tRNA molecules.

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