It is the loving thing to do for the sick sibling.
Somatic cell therapy
The health of their patients is a doctor's first consideration.
Somatic cell therapy can also help people with cancer.
It only affects the individual receiving treatment, posing no risk to future generations.
Germ line therapy
By changing the germ line, scientists prevent the disease occurring in future generations.
It ensures that people don't suffer.
Pre-Implantation Genetic Diagnosis (PGD): for diseases
Prevent late abortions of fetuses due to diseases or conditions.
Some of the conditions that are tested for cause tremendous suffering and loss of dignity, eg Huntington's disease.
If the condition is genetic the parents may already be caring for a child with this condition.
Pre-Implantation Genetic Screening (PGS): screening for gender
Some diseases are linked to gender, eg Duchenne muscular dystrophy, which only males suffer from. Females can carry the gene. They do not suffer from the condition although a small percentage may experience mild muscle weakness.
Some parents would abort a female fetus for non-medical reasons. The screening prevents this from happening, as only male embryos are implanted.
Some say that parents have the right to choose.
Enhancement: for qualities
Humans improve themselves through education and training. Why not contribute to potential before birth?
We already improve crops and animals. Why not humans?
Evolution is a change in the inherited characteristics of a population of organisms from one generation to the next. This happens anyway and genetic enhancement is just speeding up this natural process.
Research will lead to cures for more diseases and conditions.
Embryos are currently the best source of stem cells. Stem cells could be used to grow replacement organs or cure spinal injuries and other diseases and conditions.