Repressing Plasmids, Honebee Song, and Facts About Transcriptases

Tody I Learned:
1) An important cloning consideration -- if you have a gene on a plasmid under repressor control, it's almost always a good idea to grow up the plasmid in a strain that expresses the repressor (or to co-express the repressor on the same or another plasmid). You don't want the gene to express because a) most genes are toxic when highly expressed, which lowers your plasmid yield and puts selection pressure on the bacteria to spit out or disable your plasmid, and b) expressed genes tend to mutate more, which can be a real pain downstream.

2) Honeybees are fairly vocal communicators. Or perhaps musical. They use sound to communicate, in any case, mostly but not entirely by buzzing their wings. Depending on the frequency and context, their sounds can mean a number of things, most of which amount to requesting more bees to do some task.

3) There are reverse transcriptases* that will copy both RNA and DNA templates. I didn't know that -- I thought there were only reverse transcriptases that only work on RNA and transcriptases that only work on DNA. Anyway, this is handy if you want to make lots of copies of cDNA**

Along these lines, I also learned today that, according to NEB (New England Biolabs, for the uninitiated -- a really awesome biotech company specializing in enzyme engineering with good prices and a fiercely independent mentality), transcription reactions should be run longer on short templates than on long templates. That's surprising. In almost every other context I've heard of, long templates require more time to process, which makes sense. I suspect there's some kind of piling up of enzymes that happens with short templates.

Also also, while I'm talking about transcriptases, today I learned that transcription works much better on linear DNA than on plasmids (circular DNA), because on a circular template the transcriptase will just run around and around and around, making very long transcripts of multiple copies of the plasmid. I'm pretty sure I should have known this (and may have learned it) in my last lab -- can anyone confirm or deny this?

*A transcriptase is an enzyme that "transcribes", which means it copies sequences of DNA into equivalent (reverse complementary) RNA. A *reverse* transcriptase is an enzyme that converts RNA into the equivalent (reverse complement) DNA. Reverse transcriptases are useful for turning RNAs from a sample into DNA, which is easier to work with and analyze.

**cDNA = complementary DNA, which means that it was produced from an RNA template. I think cDNA used to also stand for "cloned DNA", which didn't really mean much... can anyone else confirm this?