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  • Lydia Du & Audrey Wong

Genomic Diversity: Why does it matter?

Did you know that the human genome project was completed in 2003?  And there continue to be newer additions and advancements to it every few years or so.  For example, in December of 2013, they released a GRCh38 build of the human genome sequence.  That sounds cool and all, but there remains one problem.  If you look at the graph below, there seems to be amiss.   According to NCBI, “The human reference genome is a composite genome…Approximately 93% of the GRCh38 primary assembly (the assembled chromosomes, unlocalized and unplaced sequences) consists of sequences from 11 genomic clone libraries (a library can generally be considered a proxy for an individual’s genome)... The donor of RP11 library was an anonymous male, though analysis suggests his DNA is an African-European admixture…”  

This means that 93% comes from 11 people, and 70% from just one man.  This should be an alarming lack of genomic diversity.  Some scientists are trying to make a pangenome, which layers all the collections of genomics represented, but with 3 billion or so bases in one person and hundreds of thousands of people, you can see where things get complicated.  

Why is genetic diversity important you may ask? It means equity in healthcare, including more targeted methods of treatment.  We all know that one-size-fits all method of treatment hardly works.  For example, when we learned about mendelian diseases, they affect the population no matter the conditions if inherited.  However, there were studies that found that diseases such as X-linked G6PD deficiency and favism will only show up when the person costumes fava beans, which then cause hemolytic anemia.  

Cystic fibrosis is also a really well known mendelian disease, more prevalent in people of European descent, and not so much in people of African descent.  However, this leads to children of African descent being misdiagnosed.  According to Sirugo (1), “In Europeans, the most common causative allele is DF508 in the CFTR gene, accounting for more than 70% of cases. However, DF508 accounts for only about 29% of CF cases in people of the African diaspora” 

Not everyone responds to medications in the same way. By understanding someone's genetic makeup, doctors can choose the treatments that will work best for them.  We can help by participating in studies, and spreading awareness about this lack of representation.  That way, you can help not only yourself, but your friends, family, and community. 

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