What does sequencing involve?

Answer

Dear Bert,

It is known, among other things, that certain genes (eg BRCA genes) play a role in the development of breast cancer. Genes are pieces of DNA in the chromosomes that contain information for proteins (BRCA proteins). We know that some genes contain information for correct proteins (read: good proteins that function normally). However, there are also bad BRCA genes (and therefore also bad BRCA proteins). We speak of mutations or DNA changes in these genes. In families where breast cancer occurs, it is often the case that these bad BRCA genes are present.

A BRCA gene should be seen as a switching of building blocks (four different A, C, G and T). And these building blocks are concatenated in a certain order (this order is important). In bad BRCA genes it is possible that there are changes in this order or that there are other building blocks present (mutations).

Eg in a good BRCA gene one finds eg ACGTGTTCAACGTGCATCA.

In a bad BRCA gene one finds eg ACGTGTACAACGTGCATCA. As can be seen there is another building block present at position 7. This can lead to a bad BRCA protein.

One can check whether good or bad BRCA genes are present in a person. In the first instance one can obtain the BRCA gene or DNA from this person (starting from a few cells) and then one can determine the DNA sequence of these BRCA genes (the DNA sequence is the sequence of the building blocks or the four letters).

Determining the DNA sequence of genes is done in specialized laboratories. A frequently used method is DNA sequencing according to Sanger (the dideoxy method).

To my knowledge it is not yet possible to restore bad BRCA genes in a person (eg through gene therapy), but this may be possible in the future.

Regards,