All the Genomes

One problem with personal genomics, writes John Rennie at Smart Plant's Savvy Scientist, is that people don't have just one genome. Rather, Rennie says, people can be mosaics with various inactivated chromosomes; mothers may be chimeras, containing their fetus' DNA; and neurons, for example, appear to have rearrangements that other tissues do not. Never mind the microbiome, he adds. "The full biomedical significance of mosaicism and chimerism won’t be known for a long time," Rennie writes, later adding: "Genome sequencing costs better keep falling. We’re going to need a lot of it."