As any devotee of Antiques Roadshow can tell you, just because something has been saved doesn’t mean it’s valuable.
Now, a study of plankton shows that a well-preserved genome isn’t necessarily responsible for how vertebrate animals, including humans, are put together. Researchers in Norway and France have deciphered the genetic blueprints of a tunicate called Oikopleura dioica, a tiny member of one of the most abundant plankton types in the oceans. The animal’s compact genome contains roughly 18,000 genes — nearly as many as the human genome’s 22,000 or so, but with genes in a completely different order and less DNA stuffed in between them, the researchers report online November 18 in Science.
The finding came as something of a surprise to researchers since it’s been thought that the arrangement of genes on chromosomes helps determine how an organism’s body plan will be laid out. Humans and other vertebrates tend to have genes arranged in similar order. So do organisms such as sponges. Many researchers thought that this genomic structure was important since it was preserved over millions of years of evolution. But the tunicate genome’s scrambled gene order could indicate that other organisms’ genomes got and stayed that way without any pressure from natural selection to maintain the structure.