1 Set of hunches. 2  If a theory is a set of hunches, it means we arenât yet sure we have the answer. 3  Theories always involve an element of speculation or conjecture. 4  A theory is not just one inspired thought or an isolated idea.  A theory offers some sort of explanation.
Uracil is paired with thymine in RNA and it is paired with Adenine in DNA. In DNA transcription (from DNA to RNA), uracil pairs with adenine. in regular DNA replication adenine pairs with thymine.
Nor do we know why these phages use uracil instead of thymine, but it may play an essential role in the life cycle of these viruses. If that is the case, it would make sense for the viruses to ensure that the uracil in their DNA is not replaced with thymine.