Main Difference – RNA vs mRNA
RNA and mRNA are two molecules, which act as mediators of biological processes such as protein expression and cell signaling. Three major types of RNA is found within the cell. They are messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA). DNA carries genetic information in most of the cells. DNA is transcribed into RNA and RNA is translated into proteins; this is known as the central dogma of molecular biology. The main difference between RNA and mRNA is that RNA is the product of the transcription of genes in the genome whereas mRNA is the processed product of RNA during post transcriptional modifications and serves as the template to produce a particular amino acid sequence during translation in ribosomes.
Key Areas Covered
1. What is RNA
– Definition, Types, Function
2. What is mRNA
– Definition, Features, Function
3. What are the Similarities Between RNA and mRNA
– Outline of Common Features
4. What is the Difference Between RNA and mRNA
– Comparison of Key Differences
Key Terms: DNA, Messenger RNA (mRNA), pre-mRNA, Ribosomal RNA (rRNA), Ribosome, RNA, Transcription, Transfer RNA (tRNA), Translation
What is RNA
The ribonucleic acids are referred to as RNA. RNA carries genetic information written in DNA, mainly for protein synthesis. It is a single stranded nucleic acid, composed of RNA nucleotides. RNA nucleotides consist of a ribose sugar, phosphate group, and a nitrogenous base. The four types of nitrogenous bases found in RNA are adenine (A), guanine (G), cytosine (C), and uracil (U). The process of RNA synthesis is known as transcription. Some RNA molecules are capable of folding into a three-dimensional structure known as hairpin loops via complementary base pairing. The transcription of DNA into RNA is governed by the enzyme, RNA polymerase. RNA synthesis occurs inside the nucleus. The three major types of RNA found in the cell are messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA).
Transfer RNA (tRNA)
Transfer RNA plays a major role in protein synthesis to translate the genetic code in mRNA into a particular amino acid sequence. Since tRNA forms a hairpin loop structure, the shape of the tRNA is like a clover leaf. A specific amino acid is attached to the acceptor of the tRNA molecule. The anticodon site of the tRNA molecule is capable of recognizing the complementary codon sequence in the mRNA molecule. The specific amino acid carried by the tRNA molecule is attached to the growing polypeptide chain via a peptide bond. The 3-D structure of the tRNA molecule is shown in figure 1.
Figure 1: Structure of tRNA
Ribosomal RNA (rRNA)
Ribosomal RNA is involved in producing ribosomes, which facilitates the translation of mRNA into a particular amino acid sequence. Along with several proteins, rRNA forms the organelle known as the ribosome. A ribosome is composed of two subunits, the small subunit and the large subunit. The mRNA molecule binds to the mRNA binding site of the small subunit of the ribosome. The two subunits are found detached from each other while the ribosome is free. The binding of an mRNA molecule into the small subunit induces the binding of the large subunit of the ribosome with the small subunit. Then, the translation of the genetic code in the mRNA molecule begins and tRNA molecules recognize the codon sequences in the mRNA. The formation of peptide bonds between incoming amino acid and the existing amino acid is governed by rRNA in the ribosome. Once the polypeptide chain is released from the ribosome, the two subunits are again detached from each other. The process of polypeptide synthesis by ribosomes is shown in figure 2.
Figure 2: Translation
Some small regulatory RNA molecules can also be found in the cell. They are microRNA (miRNA), small interfering RNA (siRNA), small nuclear RNA (snRNA), and small nucleolar RNA (snoRNA). The miRNA is involved in inhibiting gene expression through RNA interference. The siRNA is also involved in the regulation of transcription of genes. The snRNA and snoRNA are involved in modifying other RNAs.
What is mRNA
The messenger RNA is referred to as mRNA. The mRNA molecules are formed by the transcription of genes, which are encoded for a particular protein. The nucleotide sequence of a gene is transcribed into a messenger RNA molecule by the enzyme, RNA polymerase. In eukaryotes, the transcribed RNA molecule is called as pre-mRNA. Pre-mRNA molecule undergoes post transcriptional modifications to produce mRNA. Eukaryotic genes are composed of exons, which are readily transcribed into the pre-mRNA molecule. These introns are removed and exons are joined together in a process called splicing. The addition of an RNA cap at the 5’ end and a poly A tail at the 3’ end of the pre-mRNA molecule protect the mRNA molecule from degradation.
Figure 3: Mature mRNA
The processed mRNA molecule is called as mature mRNA and ultimately, those mature mRNA molecules are transported into the cytoplasm in order to undergo translation. In prokaryotes, the mRNA molecule contains the exact nucleotide sequence of the gene. The structure of a typical mature mRNA molecule is shown in figure 3.
Similarities Between RNA and mRNA
- Both RNA and mRNA are single-stranded nucleic acids, made up of RNA nucleotides.
- Both RNA and mRNA contain uracil.
- Both RNA and mRNA are formed by transcription of DNA in the genome by the action of an enzyme known as RNA polymerase.
- Both RNA and mRNA are capable of forming hairpin loops.
- The main function of both RNA and mRNA is to mediate transcription and translation.
Difference Between RNA and mRNA
Definition
RNA: RNA is a type of nucleic acid containing ribose and uracil.
mRNA: mRNA is a type of RNA, which encodes for a particular amino acid sequence of a protein.
Significance
RNA: Messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA) are the three major types of RNA found in the cell.
mRNA: The mRNA is a type of RNA.
Function
RNA: RNA is involved in mediating biological processes of the cell such as protein expression and cell signaling.
mRNA: The mRNA is encoded for a particular protein. The message of a protein is sent for the translation from the nucleus via mRNA.
Conclusion
RNA and mRNA are two types of nucleic acids, mediating the protein synthesis in the cell. Both RNA and mRNA contain ribose and uracil in their structure. The three major types of RNA are mRNA, tRNA, and rRNA. The mRNA is encoded for an amino acid sequence of a specific protein. The tRNA brings specific amino acids to the ribosome during translation. The rRNA is involved in forming ribosomes, which facilitates translation. The main difference between RNA and mRNA is the role of each molecule during protein synthesis.
Reference:
1. Bailey, Regina. “What Are the Types RNA?” ThoughtCo. N.p., n.d. Web. Available here. 12 July 2017.
2. “Messenger RNA (mRNA).” Encyclopædia Britannica. Encyclopædia Britannica, inc., n.d. Web. Available here. 12 July 2017.
Image Courtesy:
1. “TRNA” (CC BY 3.0) via Commons Wikimedia
2. “Peptide syn” By Boumphreyfr – Own work (CC BY-SA 3.0) via Commons Wikimedia
3. “MRNA structure” By Daylite – Own work (Public Domain) via Commons Wikimedia
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