Messenger RNA (mRNA)

Definition

Messenger RNA (mRNA) is a single-stranded RNA molecule that carries genetic information from DNA to the ribosome, where it serves as a template for protein synthesis. It plays a crucial role in translating the genetic code into functional proteins by providing the sequence of nucleotides that dictates the order of amino acids in a polypeptide chain. mRNA is produced during transcription, where a specific segment of DNA is copied into an RNA format, allowing for the expression of genes.

5 Must Know Facts For Your Next Test

1. mRNA is synthesized in the nucleus during transcription and then transported to the cytoplasm for translation.
2. Each mRNA molecule contains codons, which are groups of three nucleotides that determine the specific amino acids to be added to the growing polypeptide chain.
3. The lifespan of mRNA molecules can vary significantly; some are quickly degraded, while others can persist for hours or even days, influencing protein production levels.
4. mRNA undergoes several modifications after transcription, including capping and polyadenylation, which help protect it from degradation and assist in translation.
5. In eukaryotic cells, mRNA must undergo splicing to remove introns and join exons together before it can be translated into protein.

Review Questions

• How does the structure of mRNA contribute to its function in protein synthesis?
  • The structure of mRNA, being single-stranded, allows it to carry genetic information from DNA and serve as a flexible template for protein synthesis at ribosomes. Its nucleotide sequence is organized into codons, each representing an amino acid, which facilitates the precise translation of genetic code into functional proteins. This structural feature enables ribosomes to read mRNA efficiently and synthesize proteins according to the genetic instructions encoded in DNA.
• Discuss the significance of post-transcriptional modifications of mRNA and how they affect its stability and translation.
  • Post-transcriptional modifications of mRNA, such as 5' capping and polyadenylation, play critical roles in protecting the mRNA from degradation and enhancing its stability. These modifications also facilitate the binding of ribosomes for translation initiation. Additionally, splicing removes non-coding regions (introns) and joins coding regions (exons), ensuring that only the relevant information is translated into protein. These processes collectively influence how effectively proteins are produced within the cell.
• Evaluate the impact of mutations in mRNA on protein synthesis and potential consequences for cellular function.
  • Mutations in mRNA can lead to various changes in protein synthesis, including missense mutations that result in an incorrect amino acid being incorporated into a protein, or nonsense mutations that create premature stop codons. Such alterations can significantly impact protein structure and function, potentially leading to diseases or dysfunctions at the cellular level. The severity of these consequences often depends on factors like the nature of the mutation, its location within the coding sequence, and whether it affects essential proteins involved in critical cellular processes.

Related terms

Transcription: The process by which the information in a gene is transferred to mRNA, serving as the first step in gene expression.

Ribosome: A molecular machine found within all living cells that facilitates the translation of mRNA into proteins by linking amino acids together.

Codon: A sequence of three nucleotides in mRNA that corresponds to a specific amino acid or a stop signal during protein synthesis.