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Individuals and populations differ in gene activity levels, not just
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Sacrifice date 25 march 2009
Much like how a person's genetic code differs from other individuals,
the level at which those genes are activated in the body differs from
one person to another, scientists have learned. And though some of those
differences in gene activity are seen between different populations -
Asians versus Europeans, for instance - more of those variations are due
to individual-level factors, further obscuring the biological meaning
The findings could also have major implications for medical research,
as differing levels of gene activity may affect one's susceptibility to
developing a disease or one's response to a particular drug. The research
was conducted at the University of Washington, and was led by Joshua Akey,
assistant professor of genome sciences, and John Storey, associate professor
of genome sciences and of biostatistics. Their findings appear in the
March issue of the American Journal of Human Genetics.
"This is exactly what makes drug development so difficult, or why
it's so hard to pinpoint an exact cause for a particular disease,"
said Akey. "People have so much variation both in their genetic information
and in how those genes are activated and regulated. We need to have a
much better understanding of human genetic and gene-expression variation
in order to better treat complex diseases and develop more effective drugs."
The researchers examined data on thousands of genes from 16 people of
European and African ancestry, cataloging the variations between those
individuals. They studied each person's levels of gene expression, which
measures how much a particular gene is activated during the process of
translating DNA into a substance called RNA, and from that into basic
proteins. The more a gene is expressed, the more "messenger"
RNA is produced, leading to formation of more proteins corresponding to
that gene. Those proteins are the building blocks that make up living
cells and tissue.
"The difference between genetic information and gene expression
is like the difference between computer hardware, which are the genes
themselves, and computer software, which tells the computer what to do
on the hardware," explained Storey. "We looked at what's happening
inside the body, beyond what's hard-wired into the genes."
Scientists have known for many years about genetic variation, in which
individual letters in the genetic code change between individuals and
between different populations. However, this study is one of the first
to look at the variation in gene activity between individuals and populations.
The researchers found many differences in gene-expression levels, and
that about 17 percent of those differences were due to population-level
differences. The vast majority of the gene-expression variation was due
to random differences between individuals, and was not tied to ancestral
population or biological "race."
"It's important to remember that differences between population
groups are much less abundant than those you would see if you just compared
two randomly selected individuals," said Storey. "This means
that populations have a lot more similarities than differences when it
comes to gene expression."
Their findings may help us better understand how human populations are
structured and interrelated, and could also help explain evolutionary
development of humans from our ancient ancestors to present day. The research
may also help us understand why some people are more susceptible than
others to complex genetic diseases.
Source: University of Washington
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