Large stretches of many genomes consist of short, endlessly repeated sequences known as satellite DNA, long dismissed as junk. A study led by Madhav Jagannathan in ETH Zurich's Department of Biology, with doctoral student Lena Skrutl as lead author, now shows these repeats act as molecular barcodes that help matching chromosomes recognise one another during egg cell formation in fruit flies. The work appears in Nature Communications.
The team selectively removed satellite repeats from fly chromosomes and watched what happened during meiosis, the cell division that produces eggs and sperm. Deleting the barcode from one chromosome pair left pairing intact, because the remaining pairs could still find their partners, but removing it from two pairs caused chromosomes to associate with the wrong partners. A protein called D1 acts as the molecular glue, reading matching barcodes and binding the correct chromosomes together.
Because satellite sequences evolve rapidly, the barcodes may also help explain how new species arise. Drosophila melanogaster and Drosophila simulans diverged only two to three million years ago, yet their repeat patterns already differ enough to cause serious pairing defects in hybrids. Whether the same mechanism safeguards chromosome distribution in humans remains untested, but the study hands supposedly useless DNA a central role in heredity.