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Where do those mutants come from anyway?

I’ve recently seen X-Men First Class, and what a trip of a movie. When wondering about who to credit for super-genes and super-powers, we would normally turn to good old Dad. It was long thought that mutations were more likely to be inherited from men. Maybe we would credit Mom, but probably only if it were a good mutation. New data from the team at University of Montreal just out this June show it might have been Dad, it might have been Mom, but chances are much better that it was really the environment. In fact it’s looking like 30:1 it was probably the environment.

The new study shows that by sequencing the human genome DNA of parents and their sons or daughters,  about 50 mutations were inherited. In contrast, over 1500 were created in the cells as they grew later. Called “somatic” mutations, this means changes in the genes that happen as the body grows, but were not, and are not inherited.

This lends credibility to one of the central themes in X-Men, that radiation forces will create mutations (rather than simply inheriting them from Dad or Mom). After seeing the human genome sequencing results, researchers understand even more clearly that mutation rates are very uneven. For experimental work in the lab, mutations are usually created by geneticists with toxins or radiation to speed things up a bit. It might sound odd, but that’s what we do.

An interesting trait in corn I’ve worked with in my genetics research, was one my mentor Barbara McClintock called X-factor. It was inherited, and sped up mutations so dramatically that each generation many of the seedlings would not even survive. I thought this was a much better route than working with toxins or radiation in the lab to create new mutants. As far as I can see, toxins and radiation are things to avoid in the lab as well as in life and our environment. The location of the X-factor trait was continuously changing, and it was highly unstable much like the transposons or jumping genes. Transposons are also inherited, and highly mutagenic and create much of the beautiful color variation seen on the surface of multicolored, spotted and striped corn kernels. While I was able to work with the transposon strains of corn for a few years, the X-factor plants did not survive. The mutation burden was really too high.

The genes for X-factor and for transposons are fascinating. And if we ever have an X-Women movie, I’m going to suggest they give up on the radiation bit and just go for the inherited, super mutating gene, X-factor.

To read the original article on human mutation posted online at Nature Genetics June 12:

Variation in genome-wide mutation rates within and between human families.

the 1000 Genomes Project, Conrad DF, Keebler JE, Depristo MA, Lindsay SJ, Zhang Y, Casals F, Idaghdour Y, Hartl CL, Torroja C, Garimella KV, Zilversmit M, Cartwright R, Rouleau GA, Daly M, Stone EA, Hurles ME, Awadalla P.

Nat Genet. 2011 Jun 12. doi: 10.1038/ng.862. [Epub ahead of print]