Re: how did scientists know the recognition site of a restiction enzyme?

The Human Sequencing Project (or any kind of sequencing project) is possible mainly due to the "invention" of the dideoxy sequencing technique by Frederick Sanger 1962 for which he won a Nobel Prize in 1980 (his second). Sanger's technique is used on a large-scale in these sequencing projects through automation and lots of computer power. For more information on how this is done, see DNA Interactive: Manipulation: sorting and sequencing.

Although Sanger's technique is the most popular, it is not the only way DNA can be sequenced. Arber, Nathans and Smith did most of their work in determining what restriction enzymes do and how they do it in the late 60's. They won the Nobel prize for this work in 1978. The trio would have known about and used Sanger's technique to determine the DNA sequence of restriction enzyme binding sites. Alternatively, there are other more "tedious" ways to determine the sequence of DNA, which were used before the Sanger technique.

So restriction site sequence did not need the Human Sequencing Project.