Difference Between mRNA, tRNA and rRNA

What are mRNA, tRNA and rRNA?

mRNA

This is also called as a messenger Ribonucleic Acid. It was first discovered by Jacob, Brenner and Meselson in 1961 in California. The mRNA acts as a carrier of genetic information of the DNA from the nucleus to the ribosome. A cell consists of around 1,000 to 10,000 different species of messenger RNA. Messenger RNA genetically transmitted information is in the form of chain of nucleotides, which are organised into codons having three base pairs each.

tRNA

This is also known as a transfer RNA and it was formerly referred to as sRNA, for soluble RNA. It belongs to nucleic acid family called ribonucleic acids. The job of tRNA is to decode or translate the language of RNA into the amino acid sequence of proteins. In other words, tRNA is a type of RNA molecule that acts as the carrier of amino acids to the ribosome.  Transfer RNA adapt the messenger RNA nucleotide series into a protein’s peptide. This is the reason it is called adaptor molecule. It is between 70 to 90 nucleotides in length.  tRNA was first discovered by Francis Crick.

rRNA

rRNA, also termed as Ribosomal ribonucleic acid, is the RNA component of the ribosome. It forms an association with protein to form ribosome. It represents seventy percent of cellular RNA and is found in ribosome and nucleolus. rRNA has two types of ribosomes, the Large subunit (LSU) and the small subunit (SSU). It composes 60% of ribosome by weight and plays a critical role in identifying conserved fractions of mRNA and tRNA. It is important for protein synthesis in all the living organisms. rRNA are of ancient origin and can be found in all forms of life.

                     Figure 1. Structure of different types of RNA (Turner, Sugimoto & Freier, 1988).

Difference between mRNA, tRNA and rRNA

1. Definition

mRNA

It is a subtype of RNA which transfers a fraction of DNA code to other sections of the cell for processing. Messenger RNA is a molecule of RNA which is synthesized inside the nucleus from a DNA of a gene and finds its way into the cytoplasm, where its protein is translated by the activity of the ribosomes.

tRNA

Transfer ribonucleic acid is a type of RNA molecule that transfers protein subunits called amino acids to ribosomes for incorporation into a polypeptide undergoing synthesis.  Its main function is to deliver amino acids for protein construction.

rRNA

It is the ribosomal RNA which acts as a protein factory for cells. It forms part of the protein synthesizing organelle called ribosome, which is around sixty percent rRNA and forty percent protein by weight, or three by five (3/5) of ribosomal mass.

2. Shape

mRNA

Messenger RNA (mRNA) is single stranded and linear in shape. It is prevented from folding or rolling up so that ribosomes can attach and interpret proteins from it.

tRNA

Transfer RNA (tRNA) is complex cloverleaf shaped structure. It shows the 3D L-shaped structure by means of coaxial stacking of the helices.

rRNA

Ribosomal RNA is found in the ribosomes and is usually sphere shaped. It holds the structure of ribosome intact.

3. Function

mRNA

The messenger RNA transfers the genetic information from transcript DNA codes to the ribosomes present in the cytosol. mRNA is the most heterogenous of the 3 categories of RNA.

tRNA

The transfer RNA reads the message of nucleotides or the nucleic acids and translate it into amino acids.  It basically supplies amino acid molecules to the ribosomes required for the protein synthesis and translates messenger RNA from a binary code to a physical polypeptide.

rRNA

Ribosomal RNA are molecules associated with protein synthesizing organelles known as ribosomes. rRNA are complex constitution physically moving along a messenger RNA unit, accelerating the congregation of amino acids into protein series. rRNA also bind tRNAs and other accessory units required for protein synthesis.

4. Size

mRNA

Thread like mRNA has a size of about 400 to 12,000 nucleotides.

tRNA

Transfer RNA is 76 to 90 nt in size, which serves as the linkage between the messenger RNA and the amino acid chain of proteins.

rRNA

The ribosomal RNA consists of two subunits of ribosome, the large subunit (LSU) and Small subunit (SSU). The large subunit has ribosomal RNA of sizes 5S, 5.8S and 28S. The SSU i.e. the Small Subunit consists of ribosomal RNA of 18S size (here S stands for rRNA size)

5. Codon / Anticodon

mRNA

Messenger RNA consists of codons which code for peptide chain.

tRNA

Transfer RNA possesses anticodon on the “tip” and the analogous “amino acid” on the tail.

rRNA

Codon or anticodon sequence is absent in ribosomal RNA.

Summary

The points of difference between mRNA, tRNA and rRNA have been summarized below: