Nearly Half of the Human Genome Comes From Jumping DNA

About half of human DNA comes from jumping genes, old mobile DNA that copied itself through our genome; most are inactive today.

Medicine

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A surprising amount of the human genome is made from transposable elements, pieces of DNA that have been able to copy or move themselves around genomes over evolutionary time. Modern research estimates that at least 46 percent of the human genome is derived from these elements. They include LINEs, SINEs, LTR elements and older DNA transposons. Most of the copies in modern humans are no longer able to move, but they remain as molecular fossils of ancient activity. Some transposable elements can still affect the genome, and researchers continue to find ways these sequences can influence gene regulation, RNA processing and genome evolution. This also makes the phrase junk DNA more complicated than it sounds. DNA that does not directly code for a protein is not automatically useless, because some non-coding sequences regulate genes or affect how DNA is organized. At the same time, not every non-coding sequence has a known function, so scientists still cannot assign a useful role to every stretch of the genome. The big picture is that a large fraction of our DNA carries the history of mobile genetic elements, while the biological importance of individual sequences varies considerably.

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