mutation and glycerol stock - (Jul/09/2007 )

Hello,
Surprising my plasmid glycerol stock stored at -80C got mutated!
How is this possible? Does DNA at -80C get mutated? That was my only plasmid stock tube.....
But now atleast I would like to know is this common, has anyone encountered this??

Solution

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Mutation ? Never encountered this problem. Where is the mutation? Sure no one mixed things up.

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The stock was ok until recently when it started giving low yields...

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How many times did you freeze and thaw your stock?

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hmmm.......whenever required.....maybe 3-4 times.....

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And for how long?

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10-15 minutes

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Yeah, it happens sometimes. Well, not necessarily a confirmed mutation, but things can change somehow. Maybe it happens when they're subbed out of teh glycerol and grown... who knows. But it can happen, that's for sure. We do a lot of protein expression work, and sometimes, when we have an BL21 expression strain stored at -80oC, it will not express like it did when it was put down. Sometimes they wont express at all. All you can do is start again!

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We try very hard to never thaw our -80 stocks. You can streak a plate or inoculate a culture without thawing the stock, simply by scraping a bit of the ice with a loop.

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I had the same problem although i didn't thaw my E.coli glycerol stock. I scarped a bit of ice and streak on a plate. They are giving lower plasmid yield. I have to screen for a few colony to get a better yield colony. I am wonder why this happen?

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