The genome of a particular organism is composed of a set of genes that are coded for proteins. The process of the production of a polypeptide chain of a functional protein is known as protein synthesis. Transcription and translation are the two steps of protein synthesis. Generally, the genome occurs inside the nucleus. Therefore, transcription occurs inside the nucleus, producing a mRNA molecule based on the information of a gene. However, translation occurs in the cytoplasm. Therefore, there should be a way to carry the information of a gene into the cytoplasm. Therefore, the mRNA molecule carries the information into the cytoplasm for the production of a functional protein.
Key Areas Covered
1. What is mRNA
– Definition, Features, Role
2. How Does mRNA Molecule Carry Information from DNA
– Transcription, Translation
Key Terms: DNA, Genes, mRNA, Protein Synthesis, Transcription, Translation
What is mRNA
Messenger RNA (mRNA) is a transcript of a gene, which is encoded for a functional protein. The process that synthesizes an mRNA is known as transcription. The enzyme involved in the transcription is RNA polymerase. In eukaryotes, the primary mRNA transcript is known as pre-mRNA and it is processed to produce a mature mRNA during post-translational modifications including 5′ cap addition, editing, and polyadenylation. The incorporated introns are removed during RNA splicing. The structure of eukaryotic mRNA is shown in figure 1.
Figure 1: Eukaryotic mRNA
Since prokaryotic genes are arranged in clusters, they produce a single mRNA molecule that produces several functionally-related proteins during translation.
How Does mRNA Molecule Carry Information from DNA
Transcription is the process of encoding the information in a gene into a mRNA molecule. It occurs inside the nucleus. Transcription is initiated with the binding of RNA polymerase to the promoter of the gene. This binding is facilitated by transcription factors in both prokaryotes and eukaryotes. RNA polymerase reads the antisense DNA strand in 3′ to 5′ direction and adds complementary RNA nucleotides to the antisense strand from the transcription initiation site in 5’to 3′ direction. The addition of nucleotides is stopped at the transcription termination site. The process of transcription is shown in figure 2.
Figure 2: Transcription
The synthesized mRNA leaves the nucleus and come to the cytoplasm in order to be subjected to translation. The translation of mRNA occurs in the cytoplasm with the help of ribosomes, decoding the nucleotide sequence in the mRNA into an amino acid sequence of a protein. Therefore, mRNA serves as the carrier molecule for the information of a gene required by the production of a functional protein.
Conclusion
The mRNA is the transcript of a gene synthesized during transcription. Transcription occurs inside the nucleus. The mRNA is composed of RNA nucleotides that are decoded in the cytoplasm to produce a polypeptide chain of a functional protein with the help of ribosomes. Therefore, mRNA carries carrier information of a gene into the cytoplasm for the production of a polypeptide sequence.
Reference:
1. Venters, B J, and B F Pugh. “How eukaryotic genes are transcribed.” Critical reviews in biochemistry and molecular biology., U.S. National Library of Medicine, June 2009, Available here.
Image Courtesy:
1. “DNA transcription” By reworked and vectorized by myself – National Human Genome Research Institute, (Public Domain) via Commons Wikimedia
2. “Mature mRNA” (CC BY-SA 3.0) via Commons Wikimedia
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