Transcript

Transcription (biology) is the process by which the information in a strand of DNA is copied into a new molecule of messenger RNA (mRNA). DNA safely and stably stores genetic material in the nuclei of cells as a reference, or template. mRNA is the working copy, which carries the information to the ribosomes, the sites of protein synthesis in the cell.

Process

Transcription is performed by an enzyme called RNA polymerase. Specific sequences of DNA, known as promoters, signal the start of the gene. The polymerase binds to the promoter and begins synthesizing an mRNA molecule, using the DNA strand as a template. The sequence of the RNA molecule is determined by the sequence of the DNA strand.

Stages

Transcription can be broken down into three stages: initiation, elongation, and termination.

Initiation

In initiation, the RNA polymerase binds to the DNA strand at the promoter, and begins to unwind the DNA helix.

Elongation

During elongation, the RNA polymerase moves along the DNA strand, synthesizing an mRNA molecule.

Termination

In termination, the RNA polymerase reaches a sequence of DNA called the terminator, which signals the end of the gene. The polymerase molecule detaches from the DNA strand, and the mRNA molecule is released.

Regulation

The rate of transcription is tightly regulated by a number of factors. These include the binding of transcription factors to the promoter, and the accessibility of the promoter region due to the chromatin structure.

See also

• Translation (biology)
• Gene expression
• Central dogma of molecular biology

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