Genetic engineering in the 32nd century is quite advanced. Genes can be altered to modify most any trait desirable and then introduced to a subject through a specifically tailored virus or batch of nanomachines. While many traits like hair color, nose length, or heritable diseases are easily modified, others can be quite difficult. Taking traits from species evolved on the same planet is usually workable by most skilled geneticists. For instance, giving a human genes for cat-like ears would not be too difficult. Utilizing traits evolved in species on different worlds is vaguely possible, but typically far more work than most geneticists would consider.
Modifications have to be performed on a case by case basis, although several algorithmic models exist to handle simpler cases. It should be noted that modifying the genes of a developed subject does not evoke a rapid or complete change in most cases. A human given traits for cat-like ears would find that their human ears may grow fur over many years, but would never fully change. To complete a change, the human ears would have to be amputated and replaced through regenerative medicine, though if the changes are numerous enough, many would prefer simply introducing the genetic augmentations during the formative stages of clone development. Genetic engineering has given rise to a thriving cosmetics industry and has practically eliminated heritable disease.