Studies of prematurely old mice hint that DNA mutations underlie aging
With one look, you can usually tell whether someone is old or young. Wrinkled skin or smooth. Thinning hair or thick locks. Bifocals or Ray-Bans. These are just a few of the overt clues. Far less obvious are the age-related signs that show up on the molecular level. Ask a geneticist where to look and he may point you to a person's mitochondria. These rod-shaped residents of an animal cell provide the cell with energy, and each mitochondrion has its own DNA strand, which is distinct from the DNA in the chromosomes that dwell in the cell's nucleus. With age, this mitochondrial DNA (mtDNA) becomes riddled with mutations, both subtle and severe.