Skip to comments.Humans Show Big DNA Differences
Posted on 11/23/2006 7:09:00 PM PST by blam
Humans show big DNA differences
DNA comparisons: Gains (green), losses (red), the same (yellow)
Scientists have shown that our genetic code varies between individuals far more than was previously thought. A UK-led team made a detailed analysis of the DNA found in 270 people and identified vast stretches in their codes to be duplicated or even missing.
A great many of these variations are in areas of the genome that would not damage our health, Matthew Hurles and colleagues told the journal Nature.
But others are - and can be shown to play a role in a number of disorders.
To date, the investigation of the human genome has tended to focus on very small changes in DNA that can have deleterious effects - at the scale of just one or a few bases, or "letters", in the biochemical code that programs cellular activity.
And for many years, scientists have also been able to look through microscopes to see very large-scale abnormalities that arise when whole DNA bundles, or chromosomes, are truncated or duplicated.
But it is only recently that researchers have developed the molecular "tools" to focus on medium-scale variations of the code - at the scale of thousands of DNA letters.
This analysis of so-called copy number variation (CNV) has now revealed some startling results.
It would seem the assumption that the DNA of any two humans is 99.9% similar in content and identity no longer holds.
THE DNA MOLECULE
* The double-stranded DNA molecule is held together by chemical components called bases
* Adenine (A) bonds with thymine (T); cytosine(C) bonds with guanine (G)
* These "letters" form the "code of life"; there are about 2.9 billion base-pairs in the human genome wound into 24 distinct bundles, or chromosomes
* Written in the DNA are about 20-25,000 genes which human cells use as starting templates to make proteins; these sophisticated molecules build and maintain our bodies
The researchers were astonished to locate 1,447 CNVs in nearly 2,900 genes, the starting "templates" written in the code that are used by cells to make the proteins which drive our bodies.
This is a huge, hitherto unrecognised, level of variation between one individual and the next.
"Each one of us has a unique pattern of gains and losses of complete sections of DNA," said Matthew Hurles, of the UK's Wellcome Trust Sanger Institute.
"One of the real surprises of these results was just how much of our DNA varies in copy number. We estimate this to be at least 12% of the genome.
"The copy number variation that researchers had seen before was simply the tip of the iceberg, while the bulk lay submerged, undetected. We now appreciate the immense contribution of this phenomenon to genetic differences between individuals."
The new understanding will change the way in which scientists search for genes involved in disease.
"Many examples of diseases resulting from changes in copy number are emerging," commented Charles Lee, one of the project's leaders from Brigham and Women's Hospital and Harvard Medical School in Boston, US.
A microscope will show up the biggest code abnormalities
"A recent review lists 17 conditions of the nervous system alone - including Parkinson's disease and Alzheimer's disease - that can result from such copy number changes."
Scientists are not sure why the copy variations emerge, but it probably has something to do with the shuffling of genetic material that occurs in the production of eggs and sperm; the process is prone to errors.
As well as aiding the investigation of disease and the development of new drugs, the research will also inform the study of human evolution, which probes genetic variation in modern populations for what it can say about their relationship to ancestral peoples.
"As well as aiding the investigation of disease and the development of new drugs, the research will also inform the study of human evolution, which probes genetic variation in modern populations for what it can say about their relationship to ancestral peoples."
Maybe they'll find the Neanderthal genes lurking in there, huh?
Well, it explains the clintons. Not that they needed much explaining.
The study of variation is really where Darwin made a contribution. Ditto, Mendel. So why not focus on the correlations we can look at now rather that worry about remote ancestery? If we try hard enough we will gain knowledge far more valuable than our relationship to Chimps.
Its all a part of the same study. Why should scientists censor one part of a new and exciting field of investigation?
people need to remember DNA is three dimentionsional not jsust a straight helix. There is a ball of the DNA with RNA ziping around doing their reading and producing.
These civilian reports are usually full of holes in the real science.
Hope springs eternal. LOL
It is a matter of focus and energy , is it not? There are a relative handful of scholars who study the history of economics, more working on the present application of new data. Yes, one must look backwards, but only to make sure that it is oK to pass the car in front.
I suspect that in the end, when we have mined this field extensively, we will find a myriad of differences between individuals, base on the genes...ie each person is unique and special.
Here's the thing though---I've already seen an NPR Special that showed that genetically, the various races were non-existant.
Another lib lie?
Anyone know the real answer?
"find Neanderthal genes lurking there..."
One of the insurance companies has a whole range of commercials based on this exact premise....Every single thing the neanderthal say, proves he's a democrat.
Another lib lie?
Anyone know the real answer?
That's the problem--what is a race?
This is not a glib answer. The more one studies race, the more the concept seems to disappear.
First, there are genetic races and climatic (or geographic) races. And the two are not always related.
Genetic races track descent. Climatic races track adaption to different geographic areas. Example: Pygmies, Negritoes, and a few other small groups share the characteristics of being very small, dark-skinned, adapted to rain forests, etc. But these groups are not closely related genetically--instead, they live in similar environments.
On the other hand, a number of African groups are relate somewhat closely genetically, but differ in physical form because of long-term adaptation to local environments (Pygmy vs. Watusi).
Now, the hard part. Most of the traits which make up the geographic races are clinal, that is, varying in degree from area to area. Skin color varies from very dark in Africa to lighter in the Mediterranean area (but with tanning ability to even out summer vs. winter variations), to extremely light in the Nordic areas.
The traits defining genetic races may be either-or, rather than clines. Sticky vs. crumbly ear wax, specific fingerprint forms, etc.
Its a fascinating study.
NPR is right in a sense. There is a part of us that makes each individual, like each individual angel, a species in oneself. But we all have families; NPR is wrong in saying that there are no such things as extended families.
18:00 22 November 2006
NewScientist.com news service
Stephen Scherer, Hospital for Sick Children in Toronto Matt Hurles, Wellcome Trust Sanger Institute What makes people different may not just be their different genes, but how many copies they have of each one, and how many stretches of DNA are "missing".
Two separate studies of the human genome have revealed an unsuspected amount of variation between people in the number of copies of genes they have. Such variations appear to involve as much as 12% of our DNA, and raise questions about what constitutes a normal genome.
Originally, the differences between individuals were thought simply to be the result of mutations, whereby single bases in a DNA strand change, which can cause small changes in the proteins the DNA codes for.
Then in the 1990s scientists discovered that people also differed in the number of copies of genes they had, with large chunks of one persons DNA being duplicated or deleted when compared to anothers. Extra copies of identical genes can even cause disease with no mutation involved (see Genomics: We are all numbers).
What is normal?
How much of this duplication and deletion occurs is not clear, but now two separate groups of researchers have found that it involves more of the genome than anyone suspected.
Stephen Scherer at the Hospital for Sick Children in Toronto, Canada, and colleagues sought out differently deleted or duplicated chunks of DNA in the two complete human genome sequences so far produced. They discovered that nearly 24 million nucleotides are involved in such copy number variants (CNVs).
They conclude that adding this kind of variation to the single-base mutations we already knew about means significantly more variation exists between humans than was previously estimated.As personalised genetic sequencing becomes more common, they say, questions will be raised as to whose genome will be considered normal.
Meanwhile, Matt Hurles at the Wellcome Trust Sanger Institute in Cambridge, UK, and colleagues compared genomes from 270 people in four ethnic groups: Yoruba in Nigeria; European descendants in the US; Han Chinese in Beijing; and Japanese in Tokyo. They measured the number of copies of genes by looking at how well chunks of the genomes bonded to each other.
They found 1447 CNVs, covering about 12% of the human genome. One of the real surprises of these results was just how much of our DNA varies in copy number. We now appreciate the immense contribution of this phenomenon to genetic differences between individuals, says Hurles. Each one of us has a unique pattern of gains and losses of complete sections of DNA.
This research paper will change forever the field of human genetics, says James Lupski at the Baylor College of Medicine in Houston in the US, an independent CNV expert. Now, when seeking genetic causes for diseases, scientists will have to look, not just for mutations, but for CNVs, he says. The new data have been placed in the public domain to help researchers do this.
Journal reference: Nature Genetics (DOI: 10.1038/ng1921) Nature (vol 444, p 444)
On the contrary.
The new research was able to predict race almost perfectly from DNA.
Another law enforcement tool in DNA evidence will be to determine the race of a suspect.
It seems that the Happy Face One Worlders known as Liberals are WRONG AGAIN.
The races are significantly different right down to the molecular level, something that ANYONE with a brain could determine without indoctrination in politically-correct junk science.
I'm guessing that evolutionists are going to have to stop saying that man and chimps have 99.whatever % similiar DNA.....
A single cell has proteins that can stretch out 6 feet long. How all this is packed into a single cell is the science of protein folding.
For those that are so inclined, please visit the latest thread on the Stanford University Folding@Home distributed computing project.
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Thanks for another interesting thread.