Text I
Most Mutations in the Human Genome are Recent
and Probably Harmful to Individuals
By Kat McGowan
We really are a mutant race. Our genomes are
scattered with millions of rare gene variations, the
result of the very fast, very recent population growth
of the human species. From an estimated 5 million
individuals just 10,000 years ago, we ballooned to
more than 7 billion. On average, every duplication of
the human genome includes 100 new errors, so all
that reproducing gave our DNA many opportunities
to accumulate mutations. But evolution hasn’t had
enough time to weed out the dangerous ones: gene
variants that might make us prone to illness, or simply
less likely to survive.
Joshua Akey of the University of Washington
recently explored the average age of our species’s
gene variants, and unveiled that most are very young.
About three-quarters of single nucleotide variants — a
mutation that substitutes just one nucleotide (an A, C,
T or G) in the long string of DNA — occurred within the
past 5,000 years. This is surprising considering that
our species may be 200,000 years old. Using several
techniques to gauge the effects of these mutations,
which are the most common type of variant in the
human genome, Akey estimated that more than 80
percent are probably harmful to us.
All of these mutations — roughly 100 billion for
each generation in the entire population — potentially
accelerate the pace of evolution by giving it more raw
materials with which to work. A small percentage of
such mutations may be beneficial and may indeed help
the lives of the few individuals who carry them. For
instance, not developing wisdom teeth, producing the
right enzyme to digest milk in adulthood, being taller
than the previous generations, having lungs adapted
to living at high altitudes and being born resistant to
diseases such as HIV are some of the few recent
acquisitions of mutations in the human genome. Given
how many mutations are now circulating among living
humans, we may be evolving new capabilities already.
Akey says that determining the age and
frequency of our mutations is made possible only
by the stupendous increase in gene sequencing
speed and power. Just a few years ago, this kind of
experiment was inconceivable. Thus, only now could
we understand that the fast population growth has
littered our genomes with five times as many rare gene
variants as would be expected and such mutations
are certainly the cause of most deadly diseases we
fight against.
Available at:<http://discovermagazine.com/2013/julyaug/ 07-most-mutations-in-the-human-genome-are-recent-and- -probably-harmful>. Retrieved on: July 2013. Adapted.
In Text I, Akey explains that the stupendous progress in gene sequencing has revealed that
