For genes to be able to express themselves, an RNA molecule must be formed from a DNA molecule. This process is called transcription, and its key enzyme is the RNA polymerase. The entire process takes place in the cell's nucleus.
Initially, a DNA molecule opens at the point where the gene to be transcribed meets. This happens due to the action of RNA polymerase, which promotes the opening and exposure of the nucleotide sequences that will be transcribed. At this point, it is important to highlight that only one strand of DNA will be used for synthesis.
RNA polymerase will also guide the pairing of ribonucleotides, thus leading to elongation of the RNA strand. The nucleotides found in DNA differ from those found in RNA in that, in RNA, sugar is ribose (that's why they are called ribonucleotides) and the nitrogen base is uracil (U) instead of thymine (T).
The pairing of ribonucleotides follows the following rule:
-Uracil (U) pairs with the adenine (A) of the template tape.
-Adenine (A) pairs with the thymine (T) of the template tape.
-Cytosine (C) pairs with the guanine (G) of the template tape.
-Guanine (G) pairs with the cytosine (C) of the template tape.
In this way, a piece of DNA that contains the sequence TAGGC produces an RNA with the sequence AUCCG.
It is important to highlight that, as RNA is formed, the region of DNA that has already been transcribed closes immediately after the passage of RNA polymerase.
Transcription ends when there is termination signaling, which can be the formation of a loop in the RNA or the presence of a protein that binds to the DNA and stops the process.
by Vanessa dos Santos
Graduated in Biology
