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Into the Repeats

Some stretches of the human genome are like subdivisions in which all the houses look the same, save for the occasional identifying mailbox or broken window, writes Karen Miga from University of California, Santa Cruz, at the Scientific American Guest Blog.

"In the human genome these neighborhood blocks are equivalent to stretches of DNA that are repeated in a head-to-tail fashion over and over again with shocking uniformity," she says. "These repeats occupy millions of bases that have only occasional sites of variation within them to differentiate one repeat from another." This, she adds, makes mapping these repeated regions tricky, and they are often left as dark spots of genome maps.

However, the latest release of the human reference genome assembly, GRCh38, is starting to get a glimpse into these repeating, identical regions. This release, which Miga contributed to, includes data for one type of tandem repeats, alpha satellite DNA, which are associated with the centromere.

"While it is not yet clear why such a critical biological process associates with this peculiar repetitive landscape, the presence of new sequence models in the GRCh38 release will offer an opportunity to take a high-resolution look into the structure and function in these regions," Miga writes, later adding that "[p]ersonally, I look forward to watching the first sunrise in these blackout zones. This is the beginning of an exciting age of genome exploration."