Chloroplasts and mitochondria are, famously, the only organelles to have their own genomes, separate from that housed in the nucleus. According to a study published October 5 in Nature, it turns out that every so often, DNA escapes from mitochondria and integrates itself into our chromosomes. The findings shed light on how the nuclear genome is evolving.
Mitochondria are thought to trace their origins to a bacterium swallowed by a eukaryotic cell two billion years ago. The primitive prokaryote stuck around, whittling its genome down to just thirteen protein-coding genes in humans. Along the way, some genes simply vanished, while the rest migrated to the nucleus before we evolved from our primate ancestors. Since then, mitochondrial DNA (mtDNA) has been thought to remain separate from the nucleus, inherited wholesale from our mothers.
But in 2018, a study challenged this simple picture of maternal mitochondrial inheritance, describing paternal mtDNA in 17 ...
