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For a Plant, 98% of DNA is Just Junk

Update Date: May 13, 2013 03:13 PM EDT

Researchers have been interested in the part of human DNA that is often dubbed junk. Scientists know that within human DNA, there are three billion letters. Of these letters, only 1.5 percent of them are genes that are coded to make protein. The remaining 98.5 percent left of DNA appears to have little to no purpose at all. With the exception of some of the sequences that are believed to help with how, when and where genes are being used, the majority of this percentage is dead genes and parasitic strings of DNA. Although research into this 98 percent of junk would provide a better understanding of its role, researchers cannot experiment on the human genome in that way. Therefore, in a less controversial experiment, a new study researched the role of junk DNA in a flesh-eating water plant known as the floating bladderwort.

The research team, headed by Enrique Ibarra-Laclette from the CINESTAV institute in Mexico City and Victor Albert, a molecular evolutionary biologist from the University of Buffalo, chose to experiment on the DNA of the floating bladderwort, scientifically known as the Utricularia gibba, because this organism is known for being very minimalist. This organism contains only 82 million letters. After sequencing the genome, the research team discovered that nearly three-quarters of the DNA works to code protein, making this organism's DNA particularly junk-free in comparison to humans. Since this organism can survive without junk, it suggests that junk DNA might also be superfluous for complex organisms as well. However, since no research has been done, nothing can really be said about junk DNA in humans.

"At least for a plant, junk DNA really is just junk it's not required," Albert said."Nobody's really known what junk DNA does or doesn't do."

In their study, the researchers also discovered an interesting pattern that the floating bladderwort's DNA exhibited. They found that the floating bladderwort contained 28,500 genes, which is more than other organisms, such as grape, with larger genomes. Based on the fact that the organism appeared to have genes suggested that the entire genome was duplicated several times before the organism starting to lose the double genes that became useless. The researchers believed that the floating bladderwort experienced at least three cycles of duplications before the genes started to get smaller. The floating bladderwort now only has about three percent of repetitive pieces of DNA within its genome. In other non-minimalist plants, repetitive stretches of DNA make up anywhere from 10 to 60 percent of the genomes.  

Although the researchers are unsure as to how the floating bladderwort reached such a minimalist state, these findings provide an interesting explanation as to what the remaining 98 percent of human DNA could be. 

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