What do you mean by responsible? Do you want to know the genetics behind it, what the surface markers do, or why they are metically important? I think I can help.
a nitrogenous base, a sugar, and a phosphate. A nucleotide is the basic subunit of both DNA bad RNA. It contains a base with nitrogen, a 5-carbon sugar and a phosphate group.
Paleontology is the study of the history of life on earth as based on fossils.