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Women who are overweight while pregnant are more likely to have babies who are biologically older than those born to women of a healthy weight. This could put the babies at a higher risk of developing chronic diseases later in life, and may reduce their life expectancy. Our biological age is linked to the length of our telomeres - bits of DNA that cap the ends of our chromosomes. Our telomeres shrink every time our cells divide, and continue to shorten throughout life. "Short telomeres have been associated with cardiovascular disease, type 2 diabetes and atherosclerosis," says Tim Nawrot at Hasselt University in Belgium.

Researchers at the University of Melbourne in Australia followed 144 older people who had mild cognitive impairment for seven years. To gauge how much iron was in their brains, they measured ferritin, a protein that binds to the metal, in their cerebrospinal fluid. For every nanogram per millilitre people had at the start of the study, they were diagnosed with Alzheimer's on average three months earlier. The team also found that the biggest risk gene for Alzheimer's, ApoE4, was strongly linked with higher iron, suggesting this is why carrying the gene makes you more vulnerable.

Brain-eating amoebas (Naegleria fowleri) are found in warm freshwater pools around the world, feeding on bacteria. If someone swims in one of these pools and gets water up their nose, the amoeba heads for the brain in search of a meal. Once there, it starts to destroy tissue by ingesting cells and releasing proteins that make other cells disintegrate.

The team was grafting skin from one strain of mice to another. The new skin tended to get destroyed by the recipient animals' immune systems. But when the group injected cells from the donor mice into developing fetuses, the mice that were born were much more likely to accept the skin graft. It seemed they had been primed to the foreign cells while in the womb, and developed a tolerance.

Unborn babies can sow the seeds for rheumatoid arthritis in their mothers - and the dads might be to blame. Rheumatoid arthritis is an autoimmune disease, meaning the body's immune system turns on itself. In this case, it causes painful, swollen joints. Women are three times as likely to develop the condition as men, and seem to be especially vulnerable soon after pregnancy. A mother exchanges cells with the fetus while it is in the womb. "For most women, shortly after you give birth, the fetal cells clear up," says Giovanna Cruz, an epidemiologist at the University of California at Berkeley. "But in a subset of women they actually persist for decades." In these women, the fetal cells are effectively incorporated into their bodies, a process known as microchimerism.

As the genomes of more and more species are sequenced, geneticists are piecing together an extraordinarily detailed picture of the molecules that are fundamental to life on Earth. With modern techniques, we can not only trace how the bodies of animals have evolved, we can even identify the genetic mutations behind these changes and, as we recently reported, genes sometimes evolve in surprising ways. Here though, in celebration of the versatility of DNA, New Scientist presents five classic examples of gene evolution.

In 2012, the World Health Organisation classified colistin, the most widely used polymyxin, as being critically important for human health. But that didn't stop farmers around the world, especially in China, from using large quantities of colistin to fatten up pigs and chickens. Now Yi-Yun Liu at the South China Agricultural University in Guangzhou and colleagues have discovered the first known resistance gene for colistin that is able to move freely from one bacterium to another.

THE prospect of creating intelligent designer babies has been the subject of ethical debate for decades, but we have lacked the ability to actually do it. That may now change, thanks to a new method of testing an embryo's genes that could soon be available in some IVF clinics in the US, New Scientist can reveal.

Off with their heads. Light-averse planarian flatworms, known for their incredible ability to regenerate lost body parts, shy away from light even after they have been decapitated. This suggests they have evolved a second way to respond to light that doesn't involve eyes. Planarian flatworms, which often live in dark, watery environments shielded from direct light, don't have complex eyes like we do. But many do have two lensless, primitive "eyespots" on their heads that can detect the intensity of light.

Most colon cancers may be caused by infections with bacteria that are normally found in cows. For decades we have known that Streptococcus gallolyticus gallolyticus (SGG) is sometimes found in colon tumours, but now the microbes have been found to directly cause tumour growth in mice.

Going, going, gone. Five of the Solomon Islands have been swallowed whole by rising sea levels, offering a glimpse into the future of other low-lying nations. Sea levels in the Solomon Islands have been climbing by 7 millimetres per year over the last two decades, due to a double whammy of global warming and stronger trade winds.

The groundwater is cold, deep and twice as salty as seawater, but the water streaming out of Blood Falls, which teems with microbes, tells us that it is unlikely to be lifeless. "The fact that the [water] contains metabolically active micro-organisms that appear to be suited to life in a dark, cold brine supports the idea that life should persist throughout the subsurface," says Mikucki. If so, those microbes could be fuelling life in the Southern Ocean. By breaking down iron-containing rocks they might be dumping as much as 170 million kilograms of iron into the ocean each year, according to the researchers' estimates, helping to explain why marine productivity is seasonally very high near to the coast.

brief bios of under recognized female scientists

Graham Williams at the University of Huddersfield, UK, has a different way - to look for modifications to the twins' DNA that have come about as a result of their lifestyles. Such epigenetic changes occur when a chemical group known as a methyl group attaches to a gene and modifies the way it is expressed. This happens as a body is influenced by a person's environment, lifestyle and disease.

The activity of some of our genes varies with the seasons throughout the year. The discovery comes from an analysis of blood samples from more than 16,000 people in both hemispheres. The most striking pattern was that 147 genes involved in the immune system made it more reactive or "pro-inflammatory" during winter or rainy seasons, probably to battle the onslaught of cold and flu viruses

Predators don't control populations of their prey just by killing them. They also paint what is termed a landscape of fear, inhibiting prey from feeding and turning parts of their habitat into no-go zones. Now it appears that this has far-reaching effects throughout the food web.

What an incredible transformation. A protein used to help bones mend can also force pancreatic cells into producing insulin. The discovery could help people with type 1 diabetes produce their own insulin without having to take daily injections. In type 1 diabetes, beta cells in the pancreas that make insulin - the hormone that keeps our blood glucose levels at a safe concentration - are destroyed by the immune system. As a result, people with the disease have to inject themselves daily with insulin. Now, researchers have discovered that non-beta cells in the pancreas can be transformed into insulin-producing cells, merely by exposing them to a growth factor called BMP-7.