Category Archives: DNA

Jan. 20, 2013 In 1953, Cambridge researchers Watson and Crick published a paper describing the interweaving 'double helix' DNA structure -- the chemical code for all life.

Now, in the year of that scientific landmark's 60th Anniversary, Cambridge researchers have published a paper proving that four-stranded 'quadruple helix' DNA structures -- known as G-quadruplexes -- also exist within the human genome. They form in regions of DNA that are rich in the building block guanine, usually abbreviated to 'G'.

The findings mark the culmination of over 10 years investigation by scientists to show these complex structures in vivo -- in living human cells -- working from the hypothetical, through computational modelling to synthetic lab experiments and finally the identification in human cancer cells using fluorescent biomarkers.

The research, published January 20 in Nature Chemistry and funded by Cancer Research UK, goes on to show clear links between concentrations of four-stranded quadruplexes and the process of DNA replication, which is pivotal to cell division and production.

By targeting quadruplexes with synthetic molecules that trap and contain these DNA structures -- preventing cells from replicating their DNA and consequently blocking cell division -- scientists believe it may be possible to halt the runaway cell proliferation at the root of cancer.

"We are seeing links between trapping the quadruplexes with molecules and the ability to stop cells dividing, which is hugely exciting," said Professor Shankar Balasubramanian from the University of Cambridge's Department of Chemistry and Cambridge Research Institute, whose group produced the research.

"The research indicates that quadruplexes are more likely to occur in genes of cells that are rapidly dividing, such as cancer cells. For us, it strongly supports a new paradigm to be investigated -- using these four-stranded structures as targets for personalised treatments in the future."

Physical studies over the last couple of decades had shown that quadruplex DNA can form in vitro -- in the 'test tube', but the structure was considered to be a curiosity rather than a feature found in nature. The researchers now know for the first time that they actually form in the DNA of human cells.

"This research further highlights the potential for exploiting these unusual DNA structures to beat cancer -- the next part of this pipeline is to figure out how to target them in tumour cells," said Dr Julie Sharp, senior science information manager at Cancer Research UK.

"It's been sixty years since its structure was solved but work like this shows us that the story of DNA continues to twist and turn."

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'Quadruple helix' DNA discovered in human cells

20 January 2013 Last updated at 14:19 ET By Jonathan Amos Science correspondent, BBC News

Cambridge University scientists say they have seen four-stranded DNA at work in human cells for the first time.

The famous "molecule of life", which carries our genetic code, is more familiar to us as a double helix.

But researchers tell the journal Nature Chemistry that the "quadruple helix" is also present in our cells, and in ways that might possibly relate to cancer.

They suggest that control of the structures could provide novel ways to fight the disease.

"The existence of these structures may be loaded when the cell has a certain genotype or a certain dysfunctional state," said Prof Shankar Balasubramanian from Cambridge's department of chemistry.

"We need to prove that; but if that is the case, targeting them with synthetic molecules could be an interesting way of selectively targeting those cells that have this dysfunction," he told BBC News.

It will be exactly 60 years ago in February that James Watson and Francis Crick famously burst into the pub next to their Cambridge laboratory to announce the discovery of the "secret of life".

What they had actually done was describe the way in which two long chemical chains wound up around each other to encode the information cells need to build and maintain our bodies.

Today, the pair's modern counterparts in the university city continue to work on DNA's complexities.

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'Quadruple helix' DNA in humans

Tyrant: DNA King of Kings Tournament Semi-Finals- Masterluke vs TBake07 (1/3)

By: MasterlukePR2

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Tyrant: DNA King of Kings Tournament Semi-Finals- Masterluke vs TBake07 (1/3) - Video

HTC DROID DNA
For Extra Super Save HTC DROID DNA htcdroiddna.blogspot.com

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HTC DROID DNA - Video

C4Bomb vs Chaospig - DNA Tyrant King of Kings Tournament

By: bob dillon

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C4Bomb vs Chaospig - DNA Tyrant King of Kings Tournament - Video

Twin DNA Test
DNA testing is the most accurate method to determine if twins are identical or fraternal. Since 1994, Affiliated Genetics has performed more twin zygosity tests for physicians, researchers and the public than any other laboratory. We are one of less than 50 laboratories in the world accredited to perform relationship testing.

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Twin DNA Test - Video

DNA hydridization
Hybridization is a fundamental tool in molecular biology

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DNA hydridization - Video

irishtimes.com - Last Updated: Saturday, January 19, 2013, 12:01

The British government cannot be sure there is no safety risk from supermarket beef products that have been found to contain horse DNA, the head of the UK's leading official food control laboratory has warned.

Responding to the growing scandal over the contamination of burgers with horse and pig meat, which saw the first of the factories at the heart of the row close its production lines on Friday, the former president of the association of public analysts, Dr Duncan Campbell, said: "All we know is it is not a beefburger. What is it? We don't know. Why was it picked up in Ireland and not the UK, and how long has it been going on? Until we know what the source is of the 'horse' or 'something derived from horse' that has been found in the beef products, we cannot be sure there is no food safety risk."

Dr Campbell is the chief public analyst for West Yorkshire and a leading expert on the quality of meat. He will carry out some of the testing as the official investigation into the horsemeat scandal develops.

He said that it was "a reflex" for the UK Food Standards Agency (FSA) to say there was no food safety aspect to scandals of this sort, despite the fact that the law has clearly been broken, which may also mean that it has been broken in other ways.

Dr Campbell questioned whether raw materials could be coming from slaughterhouses that were not approved for processing meat for human consumption, or from unfit horses destined for the knacker's yard but which had instead ended up in the human food chain.

There could also be risks around residues of medicines used for sick animals but not considered safe for the human food chain, he added.

The official investigation into how large numbers of beef products on sale in the UK and Ireland came to contain horse and pig DNA is now focusing on imported ingredients added to cheap burgers.

Industry insiders have told the Guardian they believe that an ingredient called "drind", dehydrated rind or skin, may be at the heart of the scandal. It is commonly used to bulk up cheap meat products.

Additives made from boiled hide or off-cuts of carcasses are typically used to bind in added fat and water and increase the protein levels of economy beef products that have a low meat content. These may legally be identified simply as "seasoning" on the label.

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Expert warns over horse DNA

A district court judge who is a world expert in forensic DNA has called for a public debate on the use of familial DNA testing, as police reveal they have now used the "last resort" method 38 times.

Judge Arthur Tompkins, an honorary member of Interpol's DNA monitoring expert group, says there needs to be a debate about the technique - which involves crime-scene samples being compared to the national DNA databank to search for relatives of an offender - before the technique becomes even more widespread.

"The effect of it is to increase the footprint of the database without Parliament having legislated for that increased footprint," the Hamilton-based judge said.

Critics of the technique say it raises serious privacy issues and has the potential to subject entire families to "life-long genetic surveillance". It has been banned in parts of the US, where the Columbia Law Review says the practice is not "racially neutral" and has a disproportionate impact on minorities.

Police national headquarters released figures to the Sunday Star-Times showing that they have asked Environmental Science & Research (ESR) to search the DNA database for partial, familial matches on 38 occasions.

But the strike rate has been low - as a result of familial searches there were only two people convicted.

Police say the method is used only as a last resort when all other lines of inquiry have been exhausted.

Tompkins said familial testing raised many issues of privacy and ethics. "It means that you have to worry about not only what you're doing, but also what your brother and uncle and father and children do. It means that people become involved in a police investigation solely on the basis of the genetic link."

The procedure could also cause conflict within families, revealing previously unknown relationships.

Tompkins said different jurisdictions treated the technology differently - it was banned in Canada and parts of the US but used without restriction in the UK.

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Privacy fear for DNA dragnet

Charleston police Sgt. Bobby Eggleton stands on the side of U.S. 119 just outside Walton, Roane County, where police found Terry Clark's body in 1999. A DNA match through a national database has led police to her possible killer, more than 13 years after the crime was committed.

WALTON,W.Va. -- A few snowflakes rode on the breeze as Sgt. Bobby Eggleton walked across a grassy spot beside U.S. 119 south of Spencer. It was quiet, except for the hum of an occasional passing car.

Thirteen years earlier, the lifeless body of a woman lay sprawled in this grass -- naked and with the telltale marks of strangulation ringing her neck.

Eggleton stopped in the center of the wide spot by the road: "This is where we found her," the Charleston police officer said.

The woman's name was Terry Clark. She was 41 and lived in Charleston. Her killing went unsolved, and the trail turned cold.

In spring 2000, Charleston Lt. S.A. Cooper, a detective at the time, said, "We are confident -- because of the evidence we have in place -- that we may be one tip away from solving this crime."

But that tip never came . . . until now.

'She was someone we took sympathy on '

It was Memorial Day weekend 1999 when city detectives got an early morning call that said the body that had been found in Roane County was Clark, a Charleston resident.

Clark's neck was covered in marks from being strangled with a cord, and there was a wound on the back of her head from a blunt object.

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DNA links Tenn. inmate to 1999 Charleston slaying