Baloo

Its doubtful that there is any single gene in the hydra genus that is responsible for its projected immortality. There are myriad factors, not only biological but environmental as well that contribute to its longevity. Asexual reproduction is one such example. You're also talking about an organism that is only a few millimeters in length. Translating any gene to an organism as complex as a human is probably not going to do anything but give you cancer. The secret to immortality requires an integrated approach. You can't confine yourself to biological factors, and especially not to a single gene.

Thanks for you answer Max. But how do you know hairline location "involves the expression of genes during the development rather than genes being currently expressed"? I don't see how hairline is any different than thickness, color, and straightness as they relate to gene expression. Second, where do you think the greatest difficulty lies? My understanding of genome editing is that the hardest part is creating a pathway for the genes that doesn't trigger a violent (and possibly deadly) immune response.

I'm wondering if it is possible edit someone's genome (someone already living) to produce certain phenotypes, such as hair quality. Certainly, you would have to cancel out some existing genes. But I'm just wondering if its possible. Certain examples would be like manipulating hair thickness, the location of the hairline, hair color, straightness etc.