172

13.1

The Different Languages and Codes in a Cell

First, at the molecular level, we have the DNA code studied in Sect. 3.1, but of course then

the next language is RNA transcription. Interestingly, the signal to transcribe or not this

very RNA is encoded quite complexly in the DNA structure of the promoter upstream of

the transcription start of the RNA and further “upstream” (5′-end to be precise) binding

transcription factors. The next step, the translation of messenger RNA into proteins, called

translation, also uses, after all, its own language, the universal genetic code, in which the

64 possible nucleotide triplets encode the 20 (“proteinogenic”) amino acids (including

dialects that assemble proteins in organelles such as mitochondria, for example, or in bac­

teria such as mycoplasmas; freely available from NCBI at the following link: https://www.

ncbi.nlm.nih.gov/protein. This can be used to determine any protein sequence in any bio­

logical dialect).

13.1

12.7

Of course, we already know from the previous chapters that it is not quite that simple,

there are really two steps:

DNA → RNA as well as RNA (in the cell nucleus) → mRNA at the ribosome. Only

then is the mRNA translated into amino acids according to Fig. 12.7 and the genetic code.

https://com­

mons.wikimedia.org/wiki/File:Aufbau_einer_Tierischen_Zelle.jpg

13  Life Invents Ever New Levels of Language