The Search For The ‘Lost’ Genomes Of The Globe

Credit: Warren Umoh/Unsplash

Why do we lack genetic data for the majority of the earth while enormous efforts have been achieved in unlocking the mysteries of the human genome? As reported by BBC.


At the National Institutes of Health (NIH) Clinical Centre in Bethesda, Maryland, a 63-year-old Black American lady with colon cancer was given a popular chemotherapy drug called fluoropyrimidines in the summer of 2020. She was brought into intensive care, however, when she started to experience the severe side effect known as pancytopenia, which is characterised by a sharp and fast drop in red, white, and platelet counts.

This type of response is surprisingly frequent. Every year, fluoropyrimidine-based therapies are started for roughly 38,000 cancer patients in England and 154,000 patients in the US. Fluoropyrimidines save lives, but 20% to 30% of those who take them need lower doses because their bodies have trouble breaking them down. If the usual dose is administered, they have reactions that can range from severe to death.

Genetic-sequencing research

This is believed to be caused, at least in part, by variances in the human genome, the billions of letters or chemical bases that make up our DNA, similar to many adverse drug reactions. Yet, even though 99.9% of the human genome is shared by all people, the remaining 0.1% significantly varies across individuals or between ethnic groups. Changes in a gene’s underlying sequence, which can range in size from a few hundred to several million bases, can have significant effects on how we feel and function.

Genetic-sequencing research has recently made progress in understanding why some people react so negatively to fluoropyrimidines, and it has identified four distinct variants of the metabolism-related gene DPYD as the most likely culprit. Globally, healthcare organisations are now starting to sequence cancer patients’ DNA and check for each of these four mutations before deciding how much chemotherapy they should receive.

Lack of sufficient data

The only difficulty is that these experiments were done completely on white people, or as geneticists say, “individuals of European descent”. “We lack sufficient data to determine which DPYD variants are most appropriate to various ethnic groups, even though different DPYD variants may act as warning indicators for persons of other ethnicities. The majority of the time, Munir Pirmohamed, a pharmacologist at the University of Liverpool in the UK, argues that patients from ethnic minorities will receive standard doses of the medications.” “We do not know the genotype for those because, in large part, we do not know that some of these individuals will contain other ethnic-specific mutations that also impair their ability to metabolise these medications.”


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Source: BBC


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