Fishing for extra chromosomes
The first fish I ever caught was a rainbow trout. And I ate it, too. Now researchers at the USDA Agricultural Research center are working on creating genetically-modified trout that grow faster and are larger than their non-GE cousins. The modified trout have an extra chromosome: instead of the usual two, they have three. The resulting trout are unable to reproduce, and as a result, the energy that would have gone towards reproduction is shifted instead to growth.
(Somehow I think that explanation is a little too oversimplified, but there you have it nonetheless.)
In any case, researchers create these trout by mating normal trout with trout that have two extra chromosomes. Trout with four chromosomes are created by treating trout embryos with high pressure during early development. These is no risk of these “inert” trout breeding with the normal trout population, because they are infertile.
The only reason I wrote this up is because I was reminded of a condition that some women have where they posses three X chromosomes instead of the normal two. (Instances of four or five X chromosomes also occur, with each extra chromosome being increasing rare.) It’s referred to as Triple-X, and many of these women have trouble having children, though they are not all infertile. Typically these women are taller than average and may suffer some learning disabilities, though not always. There are males with an extra chromosome as well, and this condition is called Klinefelter Syndrome. As with the women, these males tend to be sterile. There have also been cases where males will have more than one excess X chromosome, but as with the women, this is quite rare.
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