The genetics of race among other lies you’ve been told

I was in my 2nd year of medical school when I jumped into a heated Facebook discussion with my consultant about using race as a proxy to stratify and diagnose patients in Malaysia. The trigger for the discussion was slightly unconventional – a TED talk by the race activist, Dorothy Roberts and my time spent studying the sociology of race and ethnicity during the summer of 2017 at Sussex. Rightfully, my consultant and several friends pointed out the flaws in my argument of outright discrediting the influence of race on health. At that time I was confused, disheartened and angry but I believe I’ve formed a more nuanced understanding of this topic which I hope to share here. Here are some facts that you should know about race, genes and health.

  • Genetic variation among humans do not cluster by racial groups i.e. there is no such thing as Malay genes, Chinese genes or Indian genes

Let’s look at our DNA (smallest units of genes) at the macro-level. Picture three colleagues of different races, one who is Malay, another who is Chinese and a third, Indian. Immediately, physical differences between these three individuals would jump out at you. With these physical differences (phenotype), it surely must also mean that the genetic make-up of the individuals (genotype) are different, right? The answer is a clear NO but the confusion is understandable.

The Human Genome Project which was completed over 3 decades ago have shown us that we humans are all 99.9% genetically identical. Our variation accounts for the 0.1% difference and this small difference shows NO racial or geographical clustering. In fact, it has been shown that there is more genetic variation between two individuals of the same race compared to two individuals of different races. That’s right – me, a Malaysian Indian with South Indian ancestry is more likely to be genetically alike when compared to a Malaysian Chinese than another Malaysian Indian.

Here’s an example of a case study by Dr. Vivian Chou (shorturl.at/ajBD3/) to illustrate this concept.

  • Single Nucleotide Polymorphisms (SNPs) can be predicted based on ANCESTRY (not race)

Although at the macro-level (in terms of alleles), there may not be clustering of variations within populations, in the micro-level (in terms of small changes in sequences of nucleotides known as SNPs), there can be clustering of variations of SNPs based on ancestry and geographical location. Most of these SNPs (which is the basis for popular DNA tests that determine your “ancestral origins”) carry no clinical significance but a small number can cause diseases.

These are mostly rare genetic diseases that cluster in people of certain ancestry and geographical locations as a result of gene flow. For example, sickle-cell anaemia which is caused by the mutation of one DNA sequence is common among people of Afro-Carribean ancestry due to the selection pressure exerted by malaria. The same concept applies to other diseases like Tay-Sachs disease and the Ashkenazi-Jews or Thalassaemia and South-East Asians. There are extensive databases for SNPs that affect the Malaysian as well as other populations.

Note that these diseases apply to people of specific ANCESTRY or geographic location, not race which is socially defined and whose definition can change over time depending on context. Taken the fact that most SNPs are of no clinical significance and those with clinical significance don’t cluster by race, using race as a proxy to determine someone’s ancestry (instead of just asking them) can be a bit misguided. Examples of Malaysian population ancestry (simplified) taken from Halim-Fikri et. al. (shorturl.at/lvBGV) as below.

Difference between race and ancestry shown below

  • Just because race does not have a genetic basis does not mean that it does not have health consequences

Throughout my clinical training, there are many times in which I was asked to highlight a patient’s race while presenting or discussing a case. I have come to an understanding that this is expected from me not because me stating the patient’s race points towards the genetic predisposition to a disease (eg. Indian genes causing diabetes – FALSE) but instead, appreciate the social, economic and behavioural impacts of race which affects health.

People of different races are treated differently in the society. Racism which leads to a constant state of residual microstress, carrying many health risks (minority stress theory) which translates to disease prevalence, morbidity, mortality and life expectancy. Other aspects like behavioural practices (eg. betel leaf chewing and tongue cancer) can also affect health but caution must be practised against overgeneralisation.

I hope this informs you and at the same time, invites you to participate in a discussion about this common misconception (or not if you contend so). The discourse on race, especially when it concerns healthcare practices is never easy but one that we should have nonetheless.

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