Messenger RNA (mRNA)

Definition

Messenger RNA (mRNA) is a type of RNA that serves as a template for protein synthesis by conveying genetic information from DNA to the ribosome. This process is essential for translating the genetic code into proteins, which perform various functions in the cell. mRNA plays a critical role in the central dogma of molecular biology, linking the information stored in genes to the production of proteins.

5 Must Know Facts For Your Next Test

1. mRNA is synthesized during transcription, where RNA polymerase reads the DNA template strand and produces a complementary RNA strand.
2. In eukaryotes, mRNA undergoes several modifications after transcription, including 5' capping, polyadenylation at the 3' end, and splicing to remove introns.
3. The sequence of nucleotides in mRNA is organized into codons, with each codon corresponding to a specific amino acid or a stop signal during protein synthesis.
4. mRNA molecules have a relatively short lifespan, being quickly degraded after translation to allow for tight regulation of gene expression.
5. In prokaryotes, translation begins while transcription is still ongoing because there is no separation between the processes due to the lack of a nuclear envelope.

Review Questions

• How does mRNA contribute to the process of protein synthesis, and what are its main roles?
  • mRNA is crucial for protein synthesis as it carries the genetic code from DNA to the ribosome, where proteins are made. Once synthesized during transcription, mRNA is translated into a sequence of amino acids at the ribosome. The codons in mRNA dictate which tRNA brings the corresponding amino acid, allowing for the assembly of proteins according to the genetic instructions encoded in the DNA.
• Discuss the differences between mRNA processing in eukaryotic and prokaryotic cells and its implications for gene expression.
  • In eukaryotic cells, mRNA undergoes extensive processing, including 5' capping, polyadenylation at the 3' end, and splicing to remove non-coding introns. This processing ensures that only mature mRNA is translated into protein. In contrast, prokaryotic cells lack these processing steps; their mRNA is directly translated as it is synthesized. This difference allows eukaryotic cells more regulation over gene expression than prokaryotes.
• Evaluate the significance of mRNA modifications and how they impact translation efficiency and stability.
  • mRNA modifications such as 5' capping and polyadenylation significantly enhance translation efficiency and stability. The 5' cap protects mRNA from degradation and assists in ribosome binding during translation initiation. Polyadenylation at the 3' end prevents rapid degradation and influences the mRNA's half-life in the cell. Together, these modifications ensure that mRNA remains functional long enough to be efficiently translated into proteins, thereby playing a vital role in regulating gene expression.

Related terms

Ribosome: A complex molecular machine found within all living cells that serves as the site of protein synthesis, translating mRNA into polypeptide chains.

Transfer RNA (tRNA): A type of RNA that helps decode mRNA sequences into proteins by bringing specific amino acids to the ribosome during translation.

Transcription: The process through which the genetic information in DNA is copied into mRNA, serving as the first step in gene expression.