Category Archives: DNA

One of the most momentous discoveries of the 20th century will be remembered this week 60 years after scientists revealed the structure of DNA.

On Thursday a memorial to British biologist Francis Crick will be unveiled by American James Watson at the university where they worked six decades ago.

Together they described the double-helix structure of DNA in a seminal paper published in the journal Nature on April 25, 1953. Their work set the stage for a molecular revolution, opening up vast new avenues of understanding about the genetic code, or "Book of Life".

Dr Watson, now retired, went on to direct the US arm of the Human Genome Project from 1988 to 1992. In 2000 the HGP published a first draft of the complete human genetic code, marking another historic turning point.

Friends, former colleagues and admirers of Professor Crick, who died in 2004, will gather at his former Cambridge University college, Gonville and Caius, to view the unveiling. The event will be followed by a series of talks and tributes by leading experts and colleagues, including Dr Watson.

Dr Watson and Prof Crick's work on the structure of DNA earned them the Nobel Prize for Medicine in 1962, which they shared with colleague Maurice Wilkins from King's College London.

The two men showed showed how DNA stored information using a four-letter molecular alphabet consisting of the letters A, T, C and G arranged in a double-helix. Three billion copies of these letters make up the entire human genome. Some are sorted into sequences called genes that provide the software instructions for making proteins and allow parental traits to be inherited.

Before the structure of DNA was unscrambled no one had a clear idea how genetic replication - one of the cornerstones of life - worked.

The discovery acted as a springboard that scientists have been jumping off ever since. Genetic research has transformed our understanding of the causes of cancer and other diseases and led to a multiplicity of new targeted treatments.

Dr Ted Bianco, acting director of the Wellcome Trust, which provided much of the funding for the Human Genome Project, said: "The discovery of the double helix is one of many great British breakthroughs in science. And we continue to be world leaders in the fields of genetics and genomics as these disciplines have grown and matured."

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DNA structure anniversary marked

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Apr. 19, 2013 Scientists have revealed how a bacterial enzyme has evolved an energy-efficient method to move long distances along DNA. The findings, published in Science, present further insight into the coupling of chemical and mechanical energy by a class of enzymes called helicases, a widely-distributed group of proteins, which in human cells are implicated in some cancers.

The new helicase mechanism discovered in this study, led by researchers from the University of Bristol and the Technische Universitt Dresden in Germany, may help resolve some of the unexplained roles for helicases in human biology, and in turn help researchers to develop future technological or medical applications.

A commonly held view of DNA helicases is that they move along DNA and "unzip" the double helix to produce single strands of DNA for repair or copying. This process requires mechanical work, so enzyme movement must be coupled to consumption of the chemical fuel ATP. These enzymes are thus often considered as molecular motors.

In the new work, Ralf Seidel and his team at the Technische Universitt Dresden developed a microscope that can stretch single DNA molecules whilst at the same time observe the movement of single fluorescently-labelled helicases. In parallel, the Bristol researchers in the DNA-Protein Interactions Unit used millisecond-resolution fluorescence spectroscopy to reveal dynamic changes in protein conformation and the kinetics of ATP consumption.

The team studied a helicase found in bacteria that moves along viral (bacteriophage) DNA. The work demonstrated that, surprisingly, the enzyme only consumed ATP at the start of the reaction in order to change conformation. Thereafter long-range movement along the DNA was driven by thermal motion; in other words by collisions with the surrounding water molecules. This produces a characteristic one-dimensional "random walk" (see picture), where the protein is just as likely to move backwards as forwards.

Mark Szczelkun, Professor of Biochemistry from the University's School of Biochemistry and one of the senior authors of the study, said: "This enzyme uses the energy from ATP to force a change in protein conformation rather than to unwind DNA. The movement on DNA thereafter doesn't require an energy input from ATP. Although movement is random, it occurs very rapidly and the enzyme can cover long distances on DNA faster than many ATP-driven motors. This can be thought of as a more energy-efficient way to move along DNA and we suggest that this mechanism may be used in other genetic processes, such as DNA repair."

The work in Bristol has been funded by the Wellcome Trust through a programme grant to Professor Mark Szczelkun from the School of Biochemistry.

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Random walks on DNA: Bacterial enzyme has evolved an energy-efficient method to move long distances along DNA

BURNABY, British Columbia, April 19 (UPI) -- Immunity to disease may vary depending on ethnicity so designing treatments that will work for everybody may be impossible, U.S. and Canadian researchers say.

DNA sequencing suggests human antibody genes and how well they operate -- and what they can fight off -- can vary from person to person, and ethnicity may influence immunity, a release from Simon Fraser University in British Columbia reported.

The researchers say the finding is based on sequencing the immensely repetitive DNA in the human genome's 1 million nucleotide-long immunoglobulin heavy (IGH)-chain locus -- long known as the most prolific producer of the 50-plus varied and diverse antibody-encoding genes that cells use to fight off infections and diseases.

"Time will confirm the extent to which this is true. But we've found that sections of the IGH-chain locus' DNA sequence are either missing or inserted into a person's genome, and this could vary depending on ethnicity," Corey Watson, a postdoctoral researcher at the Mount Sinai School of Medicine in New York, said.

That may affect the effectiveness of drugs, treatments and vaccinations usually designed to treat whole populations. The researchers said the link between antibody makeup and ethnicity surfaced when they screened the chromosomes of 425 people of Asian, African and European descent for several DNA insertions and deletions.

The findings "could mean that past environmental exposures to certain pathogens caused DNA insertions or deletions in different ethnic groups, which could impact disease risk," Watson said. "Our results demonstrate that antibody studies need to take into account the ethnicity of DNA samples used."

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DNA study suggests human immunity to disease has ethnicity basis

Mass DNA sampling has led to the jailing of a father-of-two for the shocking rape and murder of a teenaged girl in a rural part of The Netherlands 14 years ago.

A court in northern city Leeuwarden on Friday jailed farmer Jasper Steringa for 18 years for the 1999 murder of 16-year-old Marianne Vaatstra. The crime had initially been blamed on asylum seekers.

Steringa, 45, lived for 13 years less than two kilometres from the field where Vaatstra's body was found, raped, strangled and with her throat cut.

She disappeared during the night of April 30 as she returned home by bicycle from celebrating the Dutch national day, Koninginnedag.

The investigation went cold and was only reopened after changes in Dutch law last year allowed police to identify a suspect by comparing DNA found on a crime scene with genetic material indicating a family relation.

Around 7300 men turned up voluntarily in September to specially set-up DNA-testing stations in the area to have the inside of their cheeks swabbed.

One of those men was Steringa, who reportedly knew the game was up because, thanks to the change in the law, a DNA test of one of his relatives would also have identified him.

Steringa confessed to the crime and said that he hadn't handed himself in before because he wanted to see his children grow up.

'The probability of a man chosen at random having the same DNA is around one in 1,500 billion. That effectively means that the suspect's DNA is the same of Jasper S.,' the court said in a statement.

At the time of the murder, fingers were pointed at two men from Iraq and Afghanistan who had shortly before left a nearby centre for asylum seekers.

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DNA sampling nabs Dutchman for murder

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