MRNA

Definition

mRNA, or messenger RNA, is a single-stranded nucleic acid that serves as the template for protein synthesis. It is transcribed from DNA and carries the genetic information from the nucleus to the ribosomes, where proteins are made. The structure of mRNA, including its sequence and modifications, plays a critical role in determining how proteins are produced in cells.

5 Must Know Facts For Your Next Test

1. mRNA undergoes several processing steps after transcription, including capping, polyadenylation, and splicing, before it can be translated into a protein.
2. The cap structure at the 5' end of mRNA protects it from degradation and assists in the initiation of translation.
3. Polyadenylation adds a tail of adenine nucleotides to the 3' end of mRNA, which also protects the molecule and helps with the export from the nucleus.
4. During translation, ribosomes read the mRNA sequence in sets of three nucleotides (codons) to assemble amino acids into a polypeptide chain.
5. mRNA has a relatively short lifespan in cells, often being rapidly degraded after protein synthesis to ensure that proteins are made only when needed.

Review Questions

• How does the structure of mRNA facilitate its function in protein synthesis?
  • The structure of mRNA as a single-stranded nucleic acid allows it to be flexible and easily interact with ribosomes and transfer RNA (tRNA) during translation. The sequence of nucleotides in mRNA is crucial as it determines the order of amino acids in the resulting protein. Additionally, modifications like the 5' cap and 3' poly-A tail enhance its stability and translational efficiency, making it effective for carrying genetic information from DNA to ribosomes.
• What role do capping and polyadenylation play in mRNA processing, and why are these steps important?
  • Capping involves adding a modified guanine nucleotide to the 5' end of mRNA, which protects it from degradation and facilitates ribosome binding during translation initiation. Polyadenylation adds a chain of adenine nucleotides to the 3' end, providing stability and aiding in mRNA export from the nucleus. Both processes are essential for ensuring that mRNA is properly processed and functional for subsequent translation into proteins.
• Evaluate the consequences of faulty mRNA processing on protein synthesis and cellular function.
  • Faulty mRNA processing can lead to improper translation, resulting in dysfunctional or nonfunctional proteins being produced. For instance, if splicing errors occur, introns may not be removed correctly, leading to frameshift mutations that disrupt protein coding sequences. Additionally, issues with capping or polyadenylation can cause increased degradation of mRNA or failure to initiate translation altogether. These errors can significantly impair cellular function and may contribute to diseases such as cancer or genetic disorders due to misregulated protein expression.

Related terms

Transcription: The process by which the genetic information in DNA is copied into mRNA.

Ribosome: A cellular structure that facilitates the translation of mRNA into proteins by bringing together mRNA and transfer RNA (tRNA).

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