‘Junk DNA’ from million-year-old viruses actually plays vital role in human intelligence

A study released today by researchers at Lund University in Sweden indicates that inherited viruses may be responsible for creating the complex neural networks that make up the human brain.

For many years, the endogenous retroviruses that comprise about 5 percent of human DNA were thought to be “junk” – that is, sequences of DNA that do not encode protein sequences and therefore cannot self-replicate.

However, Johan Jakobsson and his colleagues at Lund University claim that these retroviruses became integrated into the transcriptional machinery of brain cells that can replicate. In fact, the researchers argue, these retroviruses play a crucial role in the basic functioning of the brain, regulating which genes are expressed and when they are allowed to do so.

“We have been able to observe that these viruses are activated specifically in the brain cells and have an important regulatory role,” Jakobsson said.

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