[From gene to disease; basic concepts].

The twenty-three pairs of chromosomes in the nuclei of human cells consist of four different components: the nucleotides adenosine, cytidine, guanosine and thymidine. Of this chromosomal DNA, 5% of the nucleotides owing to their sequence code for proteins. This involves first transcription of DNA to messenger RNA (mRNA) following which the coding part is spliced and transported from the nucleus. Translation of mRNA to amino acids takes place in the endoplasmatic reticulum. Mutations in the nucleotide sequence (deletion, insertion, duplication or substitution) lead to a change in the reading of the sequence resulting in the production of no or of different proteins (gain of function and loss of function, respectively) with possibly a disease as the consequence.