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[Bulsajo]

Study turns human genetics on its head
Research finds abnormal is really normal, puts in question some medical tests

CAROLYN ABRAHAM

From Thursday's Globe and Mail

It was nice while it lasted. But the idea that all the world's people are 99.9 per cent genetically identical -- that a mere sliver of DNA separates a Dolly Parton from a Dalai Lama -- is untrue.

An international research team has overturned the harmonious message that flowed from the Human Genome Project in 2000 and discovered more DNA differences exist among people than the experts expected.

Using new technology to study the genomes of 270 volunteers from four corners of the world, researchers have found that while people do indeed inherit one chromosome from each parent, they do not necessarily inherit one gene from mom and another from dad.

One parent can pass down to a child three or more copies of a single gene. In some cases, people can inherit as many as eight or 10 copies.

In rare instances a person might be missing a gene.

Yet despite these anomalies, they still appear to be healthy -- countering the notion of what doctors have deemed "normal" in genetics.

The work highlights how DNA helps to make each human unique, hinting that a towering basketball player, for example, might boast extra copies of a growth gene or that a daughter really might be more like her dad.

But the landmark report, published today by the journal Nature, also has disturbing implications.

It suggests that some medical tests --such as prenatal scans -- may have incorrectly flagged these kinds of genetic quirks as signs of potential defects).

However, it also makes clear that scientists have missed clues to the kinds of genetic traits that can underpin disease.

"The genome is like an accordion that can stretch or shrink . . . so you have no idea what's normal," said Steve Scherer, a senior scientist at the Hospital for Sick Children in Toronto and study co-author.

Even the number of genes people can inherit, he said, a premise set out 150 years ago by Austrian monk Gregor Mendel, the father of modern genetics, has been upended.

"We have to think of genetics in an entirely different way. We're actually more like a patchwork of genetic code than bar codes that line up evenly," Dr. Scherer said. "Everything we've been taught is different now."

The Sick Kids team worked on the project for more than two years with scientists at Harvard Medical School, the Wellcome Trust Sanger Institute in England, the University of Tokyo and the California-based Affymetrix Corp.

Their research finds that the size of at least 12 per cent of the genome -- including 2,900 genes and regions between them -- can differ dramatically between people, and in some cases, between certain ethnic groups.

The size differences are the result of DNA that is either duplicated or deleted or contains unexpected added bits of genetic code. Scientists call the phenomenon "copy number variation" or CNV for short. And it is already reshaping genetic research.

"When we're accounting for what the human genome means, there's not going to be a single human genome map that is going to be useful to one person," said Robert Hegele, a noted genetic scientist at the Robarts Research Institute in London, Ont., who read the study. "It's a huge surprise that there's so much variation of this type . . . that is so common in so many healthy people."

For this reason, scientists agree that doctors looking at less-detailed genetic tests -- such as karyotyping -- might have mistaken unusually-sized bits of DNA as signs of a medical problem.

Patients, or prospective parents receiving results of a prenatal test, for instance, might have been informed that something looked abnormal when, the new work suggests, it isn't.

While the report does not delve into the issue directly, Dr. Scherer acknowledged this is a possibility. He offered as an example a genetic test that relies on a "diagnostic probe" to evaluate the length of DNA code near the ends of chromosomes.

Shorter chromosomes, he said, are implicated in developmental delay or mental retardation due to DNA code that might be missing.

Full article, click HERE

[cbclark4]

This would be more fitting in Current Events.

Specifically at the tail end of the 185 page unabridged expose on the same topic that already appears there.

cbc

[Bulsajo]

Well then, consider me duly chastised.

Got a link?

Ah, you mean the latest Creation/Evolution thread. pass.

[Ya-ta Boy]

Very interesting article. Thanks for posting it.