1. Transcription: Inside the nucleus, the DNA sequence for a specific protein is copied into a messenger RNA (mRNA) molecule. This process is called transcription. The enzyme RNA polymerase reads the DNA sequence and uses it as a template to create a complementary mRNA molecule.
2. mRNA Processing: The newly formed mRNA molecule undergoes some processing before it leaves the nucleus. This includes:
* Capping: A protective cap is added to the 5' end of the mRNA.
* Polyadenylation: A tail of adenine nucleotides (poly-A tail) is added to the 3' end.
* Splicing: Non-coding regions of the mRNA called introns are removed, and the remaining coding regions (exons) are joined together.
3. Export: The mature mRNA molecule, now carrying the genetic code for a protein, is transported out of the nucleus through nuclear pores.
4. Translation: In the cytoplasm, the mRNA molecule binds to a ribosome. The ribosome reads the mRNA sequence in groups of three nucleotides called codons. Each codon specifies a particular amino acid.
5. Protein Synthesis: As the ribosome moves along the mRNA, transfer RNA (tRNA) molecules carrying the corresponding amino acids are recruited. The ribosome links the amino acids together in a specific order dictated by the mRNA sequence, forming a polypeptide chain.
6. Folding and Modification: The polypeptide chain then folds into a specific three-dimensional structure, forming a functional protein. This folding process may be assisted by chaperone proteins. Further modifications, such as glycosylation or phosphorylation, can also occur.
In summary, mRNA acts as a messenger carrying the protein blueprint from the nucleus to the ribosomes where the protein is synthesized. The entire process, from DNA to protein, is known as gene expression.
