Germline Cancer Mutations

Question

[adarsh_munna]

I need to know how are we getting germline mutations from blood? From where else can we get these germline mutations? Germline cells are those that form gametes, right? So how blood has this germline DNA?

[German.M.Demidov]

All human cells (that have DNA) have approx. same genetic information which a human gets from its parents (somatic mutations is a separate topic). Blood cells except red blood cells have DNA. Thus, blood cells have germline DNA.

We can detect germline mutations in any cells that have a full set of chromosomes. In addition, we can detect somatic variants in different cells from different locations, but this is beyond this question.

Answer 1

[benformatics]

This a common point of confusion that comes down to terminology reuse.

• Your somatic mutations are those acquired after conception (e.g. present in your skin from UV damage).
• Your germline mutations are those present at conception (generally it can be assumed that they would be shared with your parents). The term "germline mutations" is somewhat unrelated to your actual germline.

Your germline is the cells that give rise to your gametes. In this case, these cells would passing on some fraction of your germline mutations (but also any somatic mutations that also occurred within your germline cells).

As to your question: The germline mutations that they detect in your blood are essentially mutations that should be present in every cell of your body (obviously mutations can revert etc... but you get the picture).

[benformatics]

In theory you could acquire somatic mutations early in conception that would ultimately end up in the majority of your cells... in such a case people would probably still refer to them as germline mutations. My opinion here is that generally any mutations that cannot be clearly differentiated from other germline mutations are usually lumped together in bioinformatics.