The domain most likely to have organisms that are unicellular, have no nucleus, and contain DNA is Bacteria.

Here's why:

* Unicellular: Bacteria are single-celled organisms.

* No nucleus: Bacteria are prokaryotes, meaning they lack a membrane-bound nucleus. Their DNA is located in a region called the nucleoid, which is not enclosed by a membrane.

* Contain DNA: Like all living organisms, bacteria have DNA as their genetic material.

While Archaea also fit this description, they are generally considered a separate domain from Bacteria.