AN EXTRA copy of a gene on chromosome 21 may explain why people with Down’s syndrome are less likely to get breast and lung cancer than the rest of the population.

People with Down’s have three copies of chromosome 21 instead of two. A gene on chromosome 21 called DSCR1 is involved in controlling tumour growth. So Sandra Ryeom at the Children’s

Hospital in Boston and colleagues bred mice with three genes to find out if an extra copy gave them extra protection against cancer.

Tumours in these mice grew 50 per cent more slowly than those in healthy mice, indicating that one extra copy of the gene has a significant effect on tumour growth (Nature, DOI: 10.1038/nature08062).

To see whether this also applies

Plants thriving despite Chernobyl

MORE than two decades after the world’s worst nuclear accident, wildlife near Chernobyl in Ukraine seems surprisingly normal. “There are no dogs with two heads or interesting plant species,” says Martin Hajduch of the Institute of Plant Genetics and Biotechnology in Nitra, Slovakia.

To see how plants are able to adapt to the radiation, Hajduch compared soya in radioactive plots near Chernobyl with plants grown in uncontaminated soil. The Chernobyl soya produced different amounts of dozens of proteins, including some that aid seed production and some that defend cells from heavy metal and radiation damage (Journal of

Proteome Research, DOI: 10.1021/pr900034u ). One also protects human blood from radiation.

The results could help geneticists engineer plants that can withstand radiation in space, which may be vital for interplanetary travellers.

Komodo dragons have a secret weapon – poison

HUGE, ugly, now add venomous to the list of the Komodo

dragon ’s awful charms. The Komodo’s reputation for

hosting toxic bacteria in its mouth is undeserved: in fact

they produce a deadly venom from glands in their jaws.

For decades, wildlife documentaries have promoted

the idea that Komodo dragons owe their success as

predators to a mouthful of toxic bacteria – a claim

bolstered by a 2002 study reporting deaths among lab

mice injected with saliva. Now a team led by Bryan Fry of

the University of Melbourne, Australia, has carried out

MRI scans on a preserved Komodo head and found a

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Extra gene fights cancer in Down’s to humans, the team engineered stem cells from people with and without Down’s syndrome and injected them into mice.

They found 60 per cent fewer blood vessels surrounding tumour-like tissue grown from Down’s stem cells than those from other volunteers.

Ryeom suggests that the extra copy of DSCR1 blocks signals from the tumour that recruit vital blood vessels, and could be a potential drug target.

simpler explanation: huge venom glands (Proceedings of

the National Academy of Sciences, DOI: 10.1073/

pnas.0810883106 ). The team confirmed the finding by

removing the glands from a terminally ill Komodo.

The venom contains substances that prevent blood

clotting and widen blood vessels, which would cause a

dramatic drop in blood pressure. The dragons have sharp

teeth but a weak bite , so “it’s the venom that nails it”,

Fry says. “Prey goes into shock and can’t even struggle.”

He compares previous ignorance of the Komodo dragon’s

venomous capabilities to “missing the teeth on great

white sharks and saying they are plankton eaters”.

The study also suggests that the largest venomous

creature ever was a 5.5-metre-long ancestor of the

Komodo, the extinct Megalania lizard .

EVER felt that your backyard birds know who you are? Some may well do, as it seems mockingbirds can recognise individual people.

Doug Levey of the University of Florida in Gainesville devised a test in which one person briefly touched a northern mockingbird ’s nest four days in a row, followed by a different person on the fifth day.

The birds were quicker each day at recognising the first person as a threat, but were as slow to respond to the new person approaching their nest as they had been on the first day (Proceedings of the

National Academy of Sciences, DOI: 10.1073/pnas.0811422106 ). This ability to distinguish passers-by from potential threats may have aided the species’ success in urban areas, Levey says.

Mockingbirds can tell people apart

14 | NewScientist | 23 May 2009