system
Given the following post, respond as if you're commenting on Reddit:
human
Are Thymine, Adenine, Guanine, and Cytosine present/used in DNA of all living organisms on earth?

Are there any organisms anywhere that dont use ATCG DNA or a variation of it?
gpt
As far as I’m aware, all DNA for living things is made from ATCG on Earth. There are viruses and such that use single and double stranded RNA which contains uracil instead of thymine, but those are generally not considered to be living things.