I tend to talk about pre-implantation and artificial selection as something in the future.
It mostly is, especially in terms of hybridization, but not entirely. It is
already starting to occur.
The first goal of artificial selection is the removal of "bad" genes. Bad
genes are genes that do not work properly due to changes in their structure
caused by mutation or recombination. Sometimes bad genes are natural genes
that just cause problems for a variety of reasons.
Sickle cell anemia is an example of a gene that is advantageous in some cases,
but there is a very bad trade off in others. It can protect the carrier from
malaria, but it can also kill the carrier.
There are other traits that don't cause problems when a person is younger, but
they can fail or may be prone to cancer as the person gets older.
In any case, though much of the potential of artificial selection is in the
future, some of the knowledge and much of the basic techniques required for it
already exists and is already being used.
In one case, it was used to prevent the inheritance of a form of early onset
Alzheimers disease. In another slightly different case, it was used to insure
that one child would be a compatible donor for an older child.
In both cases, there are other moral issues raised. In the first, it was assumed
that the mother would not be capable of raising the children to maturity,
because her "bad' gene was going to leave her mentally incapacitated. In the
second case,