BIOCHEMISTRY - Key Regulators and Biological Fluids of the Human Body - 2016

3. NUCLEIC ACIDS

3.5. Transcription

The sequence of NUCLEOTIDES in DNA molecules determines the sequence of Amino Acids in protein molecules (Primary Cell/13.html">Protein Structure).

The transfer of information from DNA to protein, in accordance with the Central dogma of molecular biology, proceeds in the following direction:

Class="center">DNA -> mRNA -> protein.

The First stage involves "reading" the information encoded in DNA and transferring it to mRNA. This process is called METABOLISM/31.html">Transcription (from Latin transcriptio – copying).

Transcription is the synthesis of mRNA on the coding strand of DNA.

This process takes place in several stages.

1. The DNA unwinds.

2. The bonds between the DNA strands are broken.

3. An mRNA chain is synthesized on the coding DNA strand with the help of the enzyme RNA polymerase, following THE PRINCIPLE OF base complementarity.

If guanosine (G) is present in the transcribed DNA strand, RNA incorporates cytidine (C) into the synthesized mRNA strand; if T is present in the DNA, A is incorporated into the growing mRNA; if A is present in the DNA, U is attached instead of T (unlike Replication), since RNA always contains U instead of T in its molecule, and so on.

4. The DNA strands re-anneal.

5. The DNA rewinds.