From what I can tell, the language in these patents are exactly same with the exception of the degree of detail outlined in the claims. Claim 1, 1a, and 1b of US5693489 appear to re-phrasing claims 12, 13, and 14 through 22 from US4952496. Is US5693489 not simply a resubmission of the US4952496?
Yes - in a way the '489 patent is from a refiling of the '496 patent. Technically, the later patent was issued from an application that was a continuation of the application that resulted in the earlier patent. You can read that in the fine print on the front of the later patent.
In a continuation application the specification and drawings are generally resubmitted as-is but with different claims. Usually it is done to fight for broader or just different claims than were originally allowed. It allows the inventor to have one in the hand and a second application on the back burner. If the overlap is too large they may need to file a terminal disclaimer where both patents expire whenever the earliest one expires. This can avoid some kinds of double patenting rejections.
In this case, claim 1 of the later patent (there is only one claim) is a method for controlling the expression of a gene.
I do not see any other method with this goal.
Starting at claim 10 the methods are for: process for producing enzymatically active RNA polymerase; A process for creating vectors to supply enzymatically active DNA polymerase; and A process for inserting the DNA sequence encoding enzymatically active T7 RNA
But it is very far from my technical expertise.