What do you do with my DNA? An introduction to Genotyping

By Iain Konigsberg

Once a blood sample is submitted to the Biobank, DNA is separated from other parts of the blood. DNA stands for deoxyribonucleic acid and is made up of four different pieces that we call A, T, C, and G. Your DNA holds your genetic code and is contained within your body’s cells. Human DNA is more than 99% identical between individuals. However, there are specific areas in our DNA that are known to vary between people. For example, I may have an A where you have a T.

\We inherit our DNA from both of our parents, in the form of chromosomes. All humans have 2 copies of each chromosome. One chromosome comes from our father and the other comes from our mother. Therefore, we have two copies of every region of our DNA. This means that at one specific place in your DNA you might have two As; one A and one T; or two Ts.

These variations can be linked to important traits, such as your risk of developing a specific disease or having side effects when you take a certain medication. We can detect these types of variations through genotyping. This used to be a long process, in which researchers looked at one variation at a time. Now, we can examine variations across all of your DNA at the same time, using what are known as genotyping microarrays.

Arrays consist of a thin silicon chip with thousands of tiny wells distributed over its surface. Each well contains a marker that binds to a specific part of DNA that has a variation of interest. The marker on the chip will turn different colors, depending on your DNA (see picture). It will turn green if you have two As; turn red if you have two Ts or turn yellow if you have one A and one T. The data generated from genotyping is used to study how variations in our DNA may be related to diseases and how to treat them.

While genotyping can tell us a lot about variations in the population, it does not tell us everything. It does not look for every genetic variation that may cause disease and thus cannot be used alone to identify people who may be at risk.

Iain Konigsberg is a PhD candidate in the Human Medical Genetics & Genomics Program at the University of Colorado School of Medicine.