How is DNA purified from an agarose gel?
The agarose used in this course is of sufficient purity that DNA can be extracted from it via a variety of means and then be used in subsequent enzymatic reactions (e.g. restriction enzyme digestions, ligations, etc. ). Agarose gel electrophoresis will allow you to separate the two digested pBS fragments (what are they?) and the many (approximately how many?) yeast genomic DNA fragments derived from the restriction enzyme digestions of last week. There are a wide range of techniques used to then isolate and purify the DNA from the gel. We will be using one particularly high tech method which relies on a razor blade, a hypodermic needle, and a little bit of glass wool (see attached protocol). The DNA in TAE buffer that is eluted from the gel slice will then be further purified via precipitation in EtOH. For this and subsequent EtOH precipitations, a good rule of thumb is to add 1/10 volume (compared to the starting volume of DNA) of 3M NaOAC (pH 6.8), and at least 2.5 volumes of 95% EtO
