Many of the genes are known or suspected to play roles in stress tolerance for their original owners. Most of those strange genes have bacterial origins-thousands of species are represented within the tardigrade’s genetic makeup. “The results told us pretty unambiguously that genes that look foreign really are coming from non-animals,” Boothby says.Īll told, the tardigrade genes are made of 17.5 percent foreign material. This confirmed that what looked like foreign genes actually were just that, rather than look-a-likes developed by tardigrades themselves. “We did that for over 100 genes, with 98-percent success,” Boothby says.Ĭonvinced their reading of the genome was correct, the team then reconstructed the evolutionary ancestry of specific gene sequences. In this case, they wanted to see if they could amplify animal and bacterial genes as single units, which would only be possible if they were physically linked within the same genome. ![]() To double check, the team turned to the polymerase chain reaction, a method that amplifies targeted regions of genetic material only if they match with specific primers. ![]() “Our gut reaction was that we messed something up and must have contaminated our sample.” “When we did that, we initially saw that there were a lot of genes that looked like they didn’t come from animals,” Boothby says. Using a computer program, they stitched those sequences back together to produce the code in its entirety. To catalog every gene, he and his colleagues first extracted and sequenced many short chunks of DNA from thousands of tardigrades. “We’re beginning to realize that instead of the tree of life, it might be more appropriate to think of the web of life.”īoothby turned to the tardigrade genome in the hopes of uncovering the most basic underpinnings of the creatures’ extreme survival strategies. “When most people think of the diversity of life and flow of genetic information, they picture a tree with big branches generating smaller ones, but without any connection between the limbs,” says study leader Thomas Boothby, a Life Sciences Research Foundation postdoctoral fellow at the University of North Carolina, Chapel Hill. The bizarre mashup highlights the fact that species can take shape in much less linear ways that commonly imagined. Rather than inheriting all of their genes from their ancestors, tardigrades get a whopping one-sixth of their genetic makeup from unrelated plants, bacteria, fungi and archaeans, researchers report today in PNAS. Now scientists have discovered that tardigrades possess yet another extreme claim to fame: Their genome contains the most foreign DNA of any animal species known. They’re found on every continent including Antarctica, and they live in environments ranging from the deepest ocean trenches to the hottest deserts to the tops of the Himalaya. ![]() A dried-out tardigrade can be reanimated just by adding water-even decades later. Also known as water bears or moss piglets, the aquatic, microscopic invertebrates can survive freezing and boiling temperatures as well as the harsh conditions of outer space. Tardigrades are animals that thrive in extremes.
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