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The name of a restriction enzyme tells you where it came from…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
The name of a restriction enzyme tells you where it came from. HaeIII was isolated from Haemophilus aegyptius, and it was the third enzyme found there. BglII was isolated from Bacillus globigii, and it was the second enzyme found there.
- Say which part of the name HaeIII stands for the genus, the species and the order of isolation.
- A new enzyme is isolated from Escherichia coli. It is the first enzyme found in a strain named K. What would you call it?
- Why does the Roman number of an enzyme not tell you the number of cuts it makes?
Need a reminder? The key ideaShow
A restriction endonuclease cuts both strands inside its palindromic recognition sequence. A site of bases turns up by chance about once in bases. A straight DNA with sites gives fragments. A circular DNA with sites gives fragments.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. HaeIII, BglII, and a new enzyme from a strain K of Escherichia coli.
Plan. Use the rule: first letter of the genus, first two letters of the species, a letter for the strain if there is one, and a Roman number for the order of isolation.
Step 1. (a) In HaeIII, H is the genus Haemophilus, ae is the start of the species aegyptius, and III shows that it was the third enzyme isolated. This name has no letter for the strain.
Step 2. (b) E (Escherichia), co (coli), K (the strain) and I (the first enzyme): EcoKI.
Step 3. (c) The Roman number only gives the order in which the enzymes were isolated from that organism. The number of cuts depends on how many times the recognition sequence appears in the DNA.
Answer: (a) H genus, ae species, III order; (b) EcoKI; (c) the Roman number shows the order of isolation only.
Watch out. The strain letter is not always present, as BglII shows.
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