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Jumping genes

Back in the ‘80s, Barbara McClintock did remarkable studies of the genome of corn, the biggest crop in the world. She found “jumping genes,” pieces of DNA that get copied naturally and then inserted into new places in the genome.

These jumping genes exist in us humans, too. A very active one is LINE-1. We have 80 to 100 copies in our personal genomes. Our standard genetic machinery reads LINE-1’s DNA and makes messenger RNA. Some of that RNA then makes several special proteins. One is an enzyme that nicks our DNA, another is an enzyme that copies all of LINE-1 as DNA back into our genome at places that it targets.

That new DNA can end up in the middle of an existing gene, possibly inactivating it or possibly creating a new gene, a new physiological function. A new function can be useful. Oops. LINE-1 appears to have generated 100 genetic diseases such as hemophilia.

As Akanksha Thawani and 3 colleagues report in the February 1st issue of the journal Nature, LINE-1 has evidently generated nearly 1/3 of our whole genome. It continues to do so. So, we shuffle our own genes. Let’s also recall that viruses naturally circulating in the wild have installed themselves over time as about 8% of our genome. Talk about genetic engineering in the wild!

This has been an outreach activity of the Las Cruces Academy, viewable at GreatSchoolsorg.

 

Vince grew up in the Chicago suburb of Berwyn. He has enjoyed a long career in science, starting in chemistry and physics and moving through plant physiology, ecology, remote sensing, and agronomy.