What is the function of mRNA (messenger RNA)?
The function of mRNA, or messenger RNA, is to carry genetic information from DNA to the ribosomes in the cytoplasm of a cell. It serves as an intermediate molecule in the process of protein synthesis, also known as translation.
To understand how mRNA functions, let's go through the process step by step:
1. Transcription: mRNA is transcribed from a specific gene sequence in the DNA. This occurs in the nucleus of eukaryotic cells or the cytoplasm of prokaryotic cells. During transcription, an enzyme called RNA polymerase reads the DNA template strand and synthesizes a complementary mRNA strand by adding nucleotides.
2. mRNA Processing: In eukaryotic cells, the newly synthesized primary mRNA undergoes several modifications before leaving the nucleus. This includes the removal of non-coding regions called introns and the addition of a protective cap (5' cap) at one end and a poly-A tail at the other end. These modifications help in the stability and recognition of the mRNA by ribosomes.
3. mRNA Export: Once processed, mRNA leaves the nucleus and enters the cytoplasm through nuclear pores. Here, it is free to interact with ribosomes for protein synthesis.
4. Translation: In the cytoplasm, ribosomes bind to the mRNA molecule and read the specific genetic code in groups of three nucleotides called codons. Each codon corresponds to a specific amino acid. The ribosome reads the codons sequentially and recruits the corresponding amino acids, thereby assembling a polypeptide chain based on the genetic information encoded in the mRNA.
5. Protein Synthesis: As the ribosome progresses along the mRNA, the polypeptide chain grows until it reaches a stop codon, which signals the end of the protein synthesis process. The newly formed polypeptide chain then folds into a functional protein.
In summary, mRNA acts as a messenger molecule that carries genetic information from DNA, allowing it to be translated into proteins. It's a crucial step in the central dogma of biology, which describes the flow of genetic information from DNA to RNA to proteins.