Tibet is an interesting place. Practically the earth's west (or east) pole, it is about 2 miles above sea level, cold, dry, and inhospitable to a large portion of the world's population. It is the highest known region on earth. The world's tallest mountain from sea level, Mt. Everest, in on its border with Nepal. If the average person were to fly there, they would probably develop immediate and severe altitude sickness, and doctors suggest that travelers to such high elevations first travel to lower elevation destinations and sleep to acclimatize to the thin air. Medical studies show that acclimatization consists of speeding up your breathing, and growing more red blood cells. At Tibet's altitude, the average person has so many red blood cells that they begin to clog your circulatory system. (At which point they clot and cause conditions requiring medical intervention.) Yet the people native to the region manage it just fine. How?
Discovery News reports that a four nation study group examined Tibetans verses lower-elevation-living Chinese people to the east of them. Participants had a blood sample drawn, genes in their blood's DNA (DNA is found in every single one of your cells) analyzed, and so on. Tibetans have more efficient hemoglobin, and it's genetic to them (as compared to a "nurtured" lifestyle difference). DNA coding for red blood cells is found in our second chromosome, and Tibetans have one variant that doesn't appear in any other population. It is a variant on EPAS1.
Presumably this evolved from living in a region very close to the "death zone" from which acclimatization is literally impossible. Those able to extract more oxygen from the thin air were better able to engage in farming, trade, and other life-sustaining activities, and had more opportunities to get married than those that spent their days panting and exhausted. People living closer to sea level would gain no real advantage from this.
And no, unfortunately the only way to gain this gene would be to be born with it. And the only way to get your children to be born with it would be to marry a Tibetan. Possibly in the future one may have this gene inserted by retrovirus.