If bacteria can mutate, is it possible to modify human DNA so we can benefit from it ( for example, before someone has

Question: If bacteria can mutate, is it possible to modify human DNA so we can benefit from it ( for example, before someone has a baby, you can change their genetics so that it is less likely to pass a genetic disease, or maybe change a person's metabolic rate)?
- Keywords:
  gene
Asked by andrei to PB on 21 Jun 2013.
- Peter Balfe answered on 21 Jun 2013:
  
  We’re mutating all the time, it’s just that we deal with it very well. Cancer arises in cases where this control breaks down.
  Pre-natal screening can help identify serious defects. Screening of the parents can check if there’s a potential problem even before the baby is conceived, leading in extreme cases to solution like IVF. But editing a human isn’t ethically defensible or possible, yet…

Question: If bacteria can mutate, is it possible to modify human DNA so we can benefit from it ( for example, before someone has a baby, you can change their genetics so that it is less likely to pass a genetic disease, or maybe change a person's metabolic rate)?