January 15, 2021

The Niche

Trusted stem cell blog & resources

How much human genetic variability is there really?

1000-genomes-consortium, genetic diversity
Image from 1000-genomes-consortium.

At a genetic level, just how much do each of us human beings vary from each other in our total genome sequence?

The number I was taught in Genetics at some point was that the genomes of any two human beings are likely to be 99.9% identical. So only about 1 out of 1,000 bp would be different. That still amounts to millions of bp differences, but are perhaps most are not functionally significant? How do you feel about that 99.9% figure?

In talking with some people who are more on top of human genetics they have generally indicated that humans are only somewhere between 99.0-99.5% identical in genomic sequences overall. Wikipedia puts this number at 99.5% if you believe encyclopedias.

Last year a team led by Carlos Bustamante reported finding a striking degree of genetic diversity just in Mexico alone.

Variance in human sequences from person to person can include so-called single nucleotide polymorphisms or SNPs as well as copy number variations (CNVs).

The extent of variability is probably a moving target as well at least in part due to another source of diversity: either developmental mutations or somatic mutations in adults. A recent piece in Science found a remarkable number of somatic mutations in apparently normal skin and some were positively selected.

When big projects like the 1,000 Genomes Project (image above) and then the 100,000 Genomes Project wrap up or even working toward having 1 million people’s genomes sequenced, perhaps we can have a much better handle on this question.

So overall having to answer right now today, how much variability do you see the human genome as having? Take our poll.

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