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SCIENCE UPDATE
Rat genome offers breakthrough for medicine
A US-led international consortium announced it had sequenced the genetic code of the rat, an achievement that should greatly speed up the quest to cure disease in humans.
As popular in the lab as it is loathed outside it, the rat becomes only the third mammal whose genome has been unravelled, after humans and mice.
“This is an investment that is destined to yield major payoffs in the fight against human disease,” said Elias Zerhouni, director of the US National Institutes of Health, which contributed 118 million dollars to the initiative.
Working out how genes can malfunction can, medical researchers hope, open the way to blocking or reversing that problem, thus fixing an array of inherited disorders.
The Norwegian brown rat is well-placed to fulfill that role, because it is already widely used for testing prototype vaccines and drugs before these treatments are cautiously tried out on apes or monkeys. The rat is also cheap and abundant and, unlike primates, does not rouse moral objections as a test animal.
A further benefit can now be added to the rodent’s advantages — knowledge about the remarkable genetic similarities, as well as vital differences, between rat and man.
A draft sequence published in the Nature, covering 90 per cent of the genome, says that Rattus norvegicus and Homo sapiens have a genetic code of almost equal size.
Man has 2.9 billion bases — the chemical “rungs” that make up the code — while the rat has 2.75 billion and its cousin the mouse has 2.6 billion, with each species having around 30,000 genes.
“Comparing the human genome with those of other organisms is the most powerful tool available to understand the complex genomic components involved in human health and disease,” said Francis Collins, director of the US National Human Genome Research Institute.
The researchers found that evolutionary pressures changed the order of many of the genes in the two genomes — something that has a big effect on the functioning of the protein-making machinery — as each species adapted to changing environments.
Diamond in the sky
Twinkling in the sky is a diamond star of 10 billion trillion trillion carats, astronomers have discovered. The cosmic diamond is a chunk of crystallised carbon, 1,500 km across, some 50 light-years from the Earth in the constellation Centaurus.
It’s the compressed heart of an old star that was once bright like our Sun but has since faded and shrunk. Astronomers have decided to call the star “Lucy,” after the Beatles song, “Lucy in the Sky with Diamonds.”
“You would need a jeweller’s loupe the size of the Sun to grade this diamond!” says astronomer Travis Metcalfe of the Harvard-Smithsonian Center for Astrophysics, who led the team of researchers that discovered it.
The diamond star completely outclasses the largest diamond on Earth, the 530-carat Star of Africa which resides in the Crown Jewels of England. The Star of Africa was cut from the largest diamond ever found on Earth, a measly 3,100-carat gem.
The huge cosmic diamond, technically known as BPM 37093, is actually a crystallized white dwarf. A white dwarf is the hot core of a star, left over after the star uses up its nuclear fuel and dies. It is made mostly of carbon.
The white dwarf is not only radiant but also rings like a gigantic gong, undergoing constant pulsations.
“By measuring those pulsations, we were able to study the hidden interior of the white dwarf, just like seismograph measurements of earthquakes allow geologists to study the interior of the Earth.
We figured out that the carbon interior of this white dwarf has solidified to form the galaxy’s largest diamond,” says Metcalfe.
Astronomers expect our Sun will become a white dwarf when it dies five billion years from now. Some two billion years after that, the Sun’s ember core will crystallise as well, leaving a giant diamond in the centre of our Solar System.
New chromosome mapping
Scientists have completed the final analysis of two more human chromosomes, packed with genetic information about cancer, diabetes and other diseases, in a major step toward developing personalized antidotes.
Chromosome 19 with nearly 1,500 genes, including ones linked to inherited high cholesterol and insulin-resistant diabetes, is the most gene-dense of those sequenced so far.
By contrast chromosome 13 has one of the lowest concentrations of genes with only 633. But they include the BRCA2 gene linked to breast cancer and others for the eye tumor retinoblastoma, bipolar disorder and schizophrenia.
“Having this sort of information out there is going to make life so much easier for a lot of people,” said Dr Andrew Dunham, of the Wellcome Trust Sanger Institute in Hinxton, England which mapped chromosome 13.
An international team of scientists has already sequenced the human genome, the complete list of coded instructions needed to make a person.
Researchers are now analyzing each of the 23 pairs of human chromosomes, strands of tightly packaged DNA, to accelerate medical research and learn how to prevent and treat genetic diseases.
The sequences of chromosomes 19 and 13, which are published in the latest edition of the science journal Nature, will be freely available on internet.
“With this high quality sequence now made freely available to the scientific community, more light will be shed on individual responses to medicine,” US Energy Secretary Spencer Abraham said in a statement.
“This will enable the development of more sensitive diagnostics for susceptibility to a wide array of important diseases,” he added.
Therapy for damaged heart
Scientists have used gene therapy in experiments to help damaged heart cells function normally again, according to a study published in Circulation, a journal of the American Heart Association.
Researchers used a virus to send a gene into heart cells of people with congestive heart failure.
The gene blocked the activity of beta-adrenergic kinase, an enzyme that is elevated in people suffering from heart failure and that contributed to the heart’s weakened ability to contract.
With the enzyme block, heart cells are able to beat normally again and they regain strength, researchers said.
Lead researcher Walter Koch of Jefferson Medical College, of Philadelphia’s Thomas Jefferson University, said he hopes similar studies will eventually make gene therapy a viable treatment for heart failure, which affect nearly five million Americans. — Sci-tech World Report
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