What is done during a transcription

1. Initiation: RNA polymerases bind to promoter molecules that are located on the areas of the genome to be copied. Before genetic information can be read at all, the double helix must be unscrewed. This happens by breaking the hydrogen bond between the base pairs.

2. Elongation: During elongation, DNA is transcribed to mRNA. The RNA polymerase migrates from 3 'to 5' and, through the addition of free ribonucleotides, synthesizes an mRNA partial strand that is complementary to the DNA (illustration of the first strand), which accordingly has a 5 '-> 3' direction.

3. Termination: During the course of transcription, the RNA polymerase encounters a terminator sequence when reading the DNA. Terminators stop the RNA polymerase and the mRNA partial strand becomes detached from the DNA.

The further process differs between prokaryotes and eukaryotes:

At Prokaryotes (Organisms without a nucleus, e.g. bacteria): the mRNA is immediately transported to the ribosomes. Translation begins even before transcription is complete. This is possible because the mRNA and ribosomes are not separated from one another by any cell membrane.
At Eukaryotes (Organisms with a nucleus, e.g. humans): Translation can only begin when the mRNA has reached the ribosomes from the nucleus. Before that happens, however, the immature mRNA (this is what it is called immediately after termination is complete) is still split. Immature mRNA is made up of exons and introns. Only the exons contain important gene segments for protein biosynthesis. The introns are now removed and the remaining exons are linked together.

In addition, the mRNA has a guanine cap at the 5 'end and a poly-adenine tail made of several adenine nucleotides at the 3' end. While the guanine cap ensures a faster transition from the cell nucleus to the cytoplasm for the now mature mRNA, the function of the poly-adenine tail has not yet been conclusively researched.

Translation follows transcription.