Berkeley -- Biologists have tracked down genes that control the handedness of snail shells, and they turn out to be similar to the genes used by humans to set up the left and right sides of the body.
The finding, reported online in advance of publication in Nature by University of California, Berkeley, researchers, indicates that the same genes have been responsible for establishing the left-right asymmetry of animals for 500-650 million years, originating in the last common ancestor of all animals with bilateral body organization, creatures that include everything from worms to humans.
"Previous studies indicated that the methods for breaking left-right symmetry in animals seem to differ widely, so there was nothing suggesting that the common ancestor of humans, snails and other bilateral organisms had a common strategy for left-right asymmetry," said Nipam H. Patel, UC Berkeley professor of integrative biology and of molecular and cell biology, and an investigator of the Howard Hughes Medical Institute.
"Indeed, scientists thought that one of the genes that is critical for setting up left-right asymmetry in vertebrates was only present in vertebrates and related groups and not in any other animals," said UC Berkeley post-doctoral fellow Cristina Grande. "But we found that gene in snails, which has a lot of evolutionary implications. This cellular pathway was present already in the ancestors of most animals."
The finding, the researchers say, could help to track down the ultimate cause of symmetry-breaking in snails and other organisms, and the cascade of gene activation that leads to complex shapes, such as coiled shells.
Despite humans' superficial symmetry - our left and right sides appear to be mirror images - we are anything but symmetric. Most people's hearts are towards the left side of the body, which means the left lung is slightly smaller to make room for the heart, and our intestines are arranged
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University of California - Berkeley