An argument among the Christian world involves whether or not being homosexual is natural, or if it is a choice. In the world where Christians say it is a sin, it is commonly known to be a choice.
What does science say?
In the world of genetics, studies have been done to test if there is a gene that indicates whether a person is gay from birth.
Epigenetics, a fairly new science, has done studies on identical twins where one is gay and one is not. In the studies, the DNA was the same but showed different epigenetic methylation. DNA methylation occurs when methyl groups are added to the DNA. This changes the function of a gene.
Because of previous studies showing no difference in the DNA (before epigenetics), the church based much of this knowledge on homosexuality being a choice. But this new evidence shows that it occurs naturally.