The gel below represents a serious of restrictions digests of a 5000 bp DNA frag

Question

The gel below represents a serious of restrictions digests of a 5000 bp DNA fragment. It was digested with two different restriction enzymes, separately and together, and then individual fragments from each enzyme digest were isolated and digested with the other enzyme. Using the data on this gel, determine the restriction map of this fragment for these two enzymes. Diagram it on the line below the gel wich is marked off in units 1000bp. Indicate the EcoRI sites with a small arrow above the line, and the HindIII sites with a small arrow below the line. The digest loaded in each lane was:

1) Eco RI digrest of entire fragment

2) Hind III digrest of entire fragment

3) Eco RI + Hind III digest

4) 2500bp Eco RI fragment digested with Hind III

5) 1500bp Eco RI fragment digested with Hind III

6) 1000bp Eco RI fragment digested with Hind III

7) 2000bp Hind III fragment digested with Eco RI

8) 1250bp Hind III fragment digested with Eco RI

9) 1000bp Hind III fragment digested with Eco RI

10) 750bp Hind III fragment digested with Eco RI

Explanation / Answer

REases and DNA methyltransferases (MTases) have been named based on an original suggestion by Smith and Nathans (3). They proposed that the enzyme names should begin with a three-letter acronym in which the first letter was the first letter of the genus from which the enzyme was isolated and the next two letters were the first two letters of the species name. Extra letters or numbers could be added to indicate individual strains or serotypes. Thus, the enzyme Hindll was one of four enzymes isolated from H aemophilus in fluenzae serotype d.The first three letters of the name were italicized. Later, a formal proposition for naming the genes encoding REases and MTases was adopted (4). When there were only a handful of enzymes known, these schemes were very useful, but as more enzymes have been found, often from different genera and species with names whose three-letter acronyms would be identical, considerable laxity in naming conventions has appeared. In addition, we now know that each major type of enzyme can contain subtypes. This especially applies to the Type II enzymes, of which more than 3500 have been characterized (5). In this paper we revisit the naming conventions and outline an updated scheme that incorporates current knowledge about the complexities of these enzymes. We describe a set of naming conventions for REases and their associated MTases.

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