Close window Published online: 21 July 2006; | doi:10.1038/news060717-18 You're only as old as your genesGenetic fingerprint could pinpoint fittest organ donors.Helen Pearson Close up: ageing can be seen in our cells, chromosomes and genes.Credit: DR GOPAL MURTI / SCIENCE PHOTO LIBRARY A fingerprint of gene activity could reveal the true 'youthfulness' of our kidneys, hearts and muscle, regardless of our biological age. The technique might one day be used to find healthy organs for transplants or to warn us of impending disease. It's hard to tell, particularly on a cellular level, whether a young and healthy body conceals...