Every time human DNA is passed from one generation to the next it accumulates 100–200 new mutations, according to a DNA-sequencing analysis of the Y chromosome.
This number — the first direct measurement of the human mutation rate — is equivalent to one mutation in every 30 million base pairs, and matches previous estimates from species comparisons and rare disease screens.
The British-Chinese research team that came up with the estimate sequenced ten million base pairs on the Y chromosome from two men living in rural China who were distant relatives. These men had inherited the same ancestral male-only chromosome from a common relative who was born more than 200 years ago. Over the subsequent 13 generations, this Y chromosome was passed faithfully from father to son, albeit with rare DNA copying mistakes.
The researchers cultured cells taken from the two men, and using next-generation sequencing technologies found 23 candidate mutations. Then they validated twelve of these mutations using traditional sequencing techniques. Eight of these mutations, however, had arisen in their cell-culturing process, which left just four genuine, heritable mutations. Extrapolating that result to the whole genome gives a mutation rate of around one in 30 million base pairs.
What are the implications? I’m short on time so I’d suggest reading this exchange between myself and Joseph from last year: