Scientists have long known that HIV can go dormant, only to emerge again later and run rampant through the body.

"We know the virus can hide out," Weinberger said. "How does it hibernate? We wanted to look at the basic components of the virus."

In the laboratory, the two created a "gutted" HIV virus, or one with molecular components removed. The scientists then looked at the components necessary for the virus to replicate.

Scientists already know that a protein called Tat is connected to HIV's ability to go dormant. After a year of work, the Princeton team identified enzymes that act on the protein. These enzymes modify, or "decorate," the protein. Together, the Tat protein and the enzymes create the cascade of chemical reactions that push HIV in and out of latency.

So far, the scientists have pin-pointed the target, but have no way, at present, to affect it.

Differences in eye colour are largely down to "single nucleotide polymorphisms" (SNPs - pronounced "snips"); variations in the sequence of letters that make up a single strand of human DNA.

SNPs represent a change of just one letter in the genetic sequence. These changes, or mutations, in our DNA can have important consequences for how the gene gets physically expressed.

All the SNPs are located near a gene called OCA2. This gene produces a protein that helps give hair, skin and eyes their colour. And mutations in OCA2 cause the most common type of albinism.

Goldman said a calendar with pictures of actress Sophia Loren at the age of 71 wearing only a pair of earrings underlined how perceptions of age had changed.

"If somebody told you 14 years ago that they were going to have a former sex symbol pose in earrings only, you would have been disgusted or you would have closed your eyes," he said. "Today she looks great at the age of 71."

Stem cell therapy will allow people to regain lost hair, remove wrinkles by renewing skins, and grow new nerves for paralyzed patients, Michael Klentze, director of the Klentze Institute of Anti-aging in Munich, Germany, told Reuters.

Stem cells have the ability to act as a repair system for the body, because they can divide and differentiate, replenishing other cells as long as the host organism is alive.

"People who have hair loss they can hope in the next months they've got new hair, not strange hair, but their own hair," he said.

Although they did not have fertility problems, the woman and her partner created embryos by IVF. This allowed doctors to remove a cell and test it for the cancer gene, so only unaffected embryos were transferred to her womb.

The couple are the first to take advantage of a relaxation in the rules governing embryo screening.

When the technique was developed in 1989 it was allowed only for genes that always cause disease, such as those for cystic fibrosis. However, it was approved last year for the eye cancer, which affects only 90 per cent of those who inherit a mutated gene.

The pregnancy will increase controversy over the procedure, which the Government’s fertility watchdog authorised on Wednesday for genes that confer an 80 per cent lifetime risk of breast and bowel cancer.

The researchers looked for genetic variations known as polymorphisms on two genes known to be associated with asthma and allergies, IL-4RA and IL-13.

People with polymorphisms on those genes were more likely to have asthma and allergies and less likely to have a glioblastoma.

"For example, we found that one genetic variant that causes a two-fold risk in asthma susceptibility reduces the risk of glioblastoma multiforme by 40 percent," said Schwartzbaum.

Why genes that promote asthma or allergies might offer protection against brain tumors is unclear, said Schwartzbaum.

She speculated that the gene variations might hinder inflammation in the brain, even though those same genes help cause inflammation in the lungs.