MRNA

Definition

mRNA, or messenger RNA, is a single-stranded molecule that conveys genetic information from DNA to the ribosome, where it serves as a template for protein synthesis. It plays a critical role in translating the genetic code into functional proteins and undergoes various processing steps to become mature mRNA before it can be translated into proteins.

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. In eukaryotic cells, mRNA undergoes several modifications, including 5' capping, polyadenylation, and splicing, to become mature and functional.
3. The genetic code is read in sets of three nucleotides (codons) on the mRNA, with each codon corresponding to a specific amino acid.
4. Prokaryotic mRNA can be translated while it is still being transcribed, allowing for rapid protein synthesis.
5. mRNA has a relatively short lifespan in cells, as it is rapidly degraded after translation to regulate protein levels.

Review Questions

• How does mRNA serve as a bridge between DNA and protein synthesis?
  • mRNA acts as the intermediary between DNA and protein synthesis by carrying the genetic information encoded in DNA to the ribosomes, where proteins are made. During transcription, RNA polymerase reads the DNA template and synthesizes a complementary strand of mRNA. This mRNA then undergoes processing before being translated into a specific sequence of amino acids at the ribosome, effectively converting genetic instructions into functional proteins.
• What are the key steps involved in the processing of pre-mRNA to mature mRNA in eukaryotic cells?
  • The processing of pre-mRNA to mature mRNA involves several key steps: first, a 5' cap is added to protect the mRNA from degradation and facilitate ribosome binding. Next, polyadenylation occurs at the 3' end, adding a tail that also helps stabilize the molecule. Finally, splicing removes non-coding regions called introns and joins together coding sequences known as exons. This processed mRNA is now ready for export from the nucleus to the cytoplasm for translation.
• Evaluate how differences in mRNA processing between prokaryotes and eukaryotes affect gene expression.
  • In prokaryotes, mRNA is typically transcribed and translated almost simultaneously since they lack a defined nucleus. This means that there is little to no processing involved; the primary transcript can be used directly for protein synthesis. In contrast, eukaryotic mRNA undergoes extensive processing steps before it can be translated. This difference allows eukaryotes to regulate gene expression more finely through mechanisms like alternative splicing and controlled degradation of mRNA. Consequently, this adds complexity and versatility to eukaryotic gene expression compared to prokaryotic systems.

Related terms

Codon: A codon is a sequence of three nucleotides in mRNA that specifies a particular amino acid or a stop signal during protein synthesis.

RNA Polymerase: An enzyme that synthesizes RNA from a DNA template during transcription, forming the primary transcript that will be processed into mRNA.

Splicing: The process of removing introns and joining exons together in the pre-mRNA to produce mature mRNA, which can then be translated into a protein.