Those units of inheritance described by Mendel back in the day, we call it today genes, which are fragments of DNA that codes for proteins transcribed by RNA and synthesized for ribosomes to form the monomers of these polymers: amino acids. And regarding the limits on how scientists manipulate the expression of genetic information, we could say that, although human being already has done it by artificial selection, and biotechnology, it could be bad when doing it with bad purposes, as the selective culturing of biologic antigens to harm the worldwide population or the usage of it in wars.