The short answer, ake, is that as the world changes it is necessary to see how the existing moral code should encompass that change. It would be silly for the church to say there is nothing in the bible or traditional teachings about genetic modification so we cannot have an opinion. No, you apply your understanding to the new area.

But moral codes do not give yes/no answers, so I am afraid a lot of stuff I was taught as a child (This is a sin, that is not) fits into the category of "When I was a child, I thought like a child. Now I am a man I have put aside childish things". Let me tell you a short tale a priest visiting from a poor backwater of India told me. He had come across cases where parents deliberately maimed their babies because they could get an income as a beggar whereas they were likely to starve any other way. "And don't tell me", he said, "that what they did was wrong or immoral."

So I am not really interesting in whether or not birth control 'is' a moral sin, since as with that infant such simple yes/no answers don't help. A discussion is another matter, as that helps us to see that simple answers won't cut it.