How is mRNA produced during transcription?

mRNA is produced during transcription when a segment of DNA is copied into RNA by the enzyme RNA polymerase.

Transcription is the first step in gene expression, where the information in a gene's DNA is transferred to a messenger RNA (mRNA) molecule. This process takes place in the nucleus of eukaryotic cells and in the cytoplasm of prokaryotes. It involves three main stages: initiation, elongation, and termination.

During initiation, the enzyme RNA polymerase binds to a specific region of the DNA called the promoter. This signals the start of the gene to be transcribed. The DNA double helix unwinds and separates to expose the gene sequence. The RNA polymerase then begins to synthesise the mRNA strand.

In the elongation phase, the RNA polymerase moves along the DNA template strand, adding complementary RNA nucleotides. This forms the mRNA molecule. It's important to note that RNA polymerase reads the DNA template from 3' to 5' direction, and synthesises the mRNA in the 5' to 3' direction. The mRNA molecule is thus a complementary copy of the DNA strand, with the exception that RNA contains uracil (U) instead of thymine (T).

Finally, in the termination stage, the RNA polymerase reaches a sequence of DNA called the terminator. This signals the end of the gene. The RNA polymerase, the mRNA molecule, and the DNA template then dissociate from each other. The mRNA molecule undergoes further processing before it is ready for translation into a protein.

In summary, the production of mRNA during transcription is a complex process that involves the precise interaction of enzymes and nucleic acids. It is a crucial step in gene expression, allowing the genetic information stored in DNA to be converted into proteins, which carry out various functions in the cell.