We Are All Mutants: Measurement Of Mutation Rate In Humans By Direct Sequencing

Human genetic drift is 1 mutation in each 30 million nucleotides each generation. We have about 3,000 million nucleotides, so each generation carries about 100 new mutations forward for each living individual.

An international team of 16 scientists today reports the first direct measurement of the general rate of genetic mutation at individual DNA letters in humans. The team sequenced the same piece of DNA - 10,000,000 or so letters or 'nucleotides' from the Y chromosome - from two men separated by 13 generations, and counted the number of differences. Among all these nucleotides, they found only four mutations.

So when all the genes are counted, your body consists of cells that contain about 100 different versions of the DNA that makes up your body. 

This number grows as we age.