Transcription

Transcription is the process by which DNA makes a copy of its message in the form of mRNA, which carries instructions to build proteins

The cell needs DNA’s instructions to make proteins, but DNA stays in the nucleus. Think of DNA as an instruction manual that never leaves the library, so the cell makes a working copy called messenger RNA, or mRNA.

Because DNA is double-stranded, it must first unwind. An enzyme called RNA polymerase attaches to the DNA and reads just one strand, letter by letter.

As RNA polymerase reads the DNA, it builds a copy in the form of mRNA. The rules are simple: A pairs with U, T with A, G with C, and C with G. Bit by bit, the mRNA strand grows, carrying DNA’s instructions.

When RNA polymerase reaches a stop signal on the DNA, it stops making mRNA. The mRNA then detaches from the DNA, is processed in the nucleus, and exits through nuclear pores to the cytoplasm for protein production.