Messenger RNA (mRNA)

Definition

Messenger RNA (mRNA) is a single-stranded molecule that carries genetic information from DNA to the ribosome, where proteins are synthesized. It plays a crucial role in the process of transcription, where DNA is transcribed into mRNA, and translation, where mRNA is translated into a specific protein. The structure of mRNA includes a sequence of nucleotides that corresponds to the amino acids in a protein, making it essential for gene expression.

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 has a specific sequence of codons, each corresponding to an amino acid or a stop signal during protein synthesis.
3. mRNA is characterized by a 5' cap and a poly-A tail at the 3' end, which help protect it from degradation and assist in translation.
4. The lifespan of mRNA varies, affecting how long the corresponding protein is produced; some mRNAs are rapidly degraded while others are stable.
5. In eukaryotic cells, mRNA undergoes splicing where introns are removed and exons are joined together before it can be translated.

Review Questions

• How does the structure of mRNA facilitate its role in protein synthesis?
  • The structure of mRNA, being single-stranded, allows it to be easily synthesized during transcription and then effectively read by ribosomes during translation. The sequence of codons in mRNA directly determines the sequence of amino acids in a protein, ensuring accurate translation of genetic information. Additionally, features like the 5' cap and poly-A tail enhance stability and translation efficiency, making mRNA an essential component in the process of gene expression.
• What are the key steps involved in the transition from DNA to protein via mRNA, including transcription and translation?
  • The transition from DNA to protein begins with transcription, where an enzyme called RNA polymerase synthesizes an mRNA strand complementary to the DNA template. Once synthesized, this mRNA is processed (including capping and polyadenylation) before being transported to the cytoplasm. During translation, ribosomes read the sequence of codons on the mRNA, facilitating the assembly of amino acids into a polypeptide chain through interactions with transfer RNA (tRNA). This entire process ensures that genetic information is accurately converted into functional proteins.
• Evaluate the implications of mRNA stability on gene expression and cellular function.
  • The stability of mRNA directly impacts gene expression and cellular function because it determines how long a particular protein is produced within the cell. Stable mRNAs can lead to prolonged protein production, which might be crucial for processes like growth or response to stress. Conversely, unstable mRNAs degrade quickly, allowing for rapid changes in protein levels in response to environmental cues. This regulation plays a critical role in cellular adaptation and functionality, underscoring the importance of mRNA dynamics in maintaining homeostasis within cells.

Related terms

Transcription: The process by which the genetic information encoded in DNA is copied into messenger RNA.

Translation: The process by which ribosomes read the sequence of mRNA and assemble amino acids into a polypeptide chain, forming a protein.

Ribosome: A molecular machine found within all living cells that performs the synthesis of proteins by translating messenger RNA.