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Old 09-12-2011, 07:07 AM   #21
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sooooooo.... what's the verdict on that fermentation?
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Old 09-12-2011, 09:04 AM   #22
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Quote:
Originally Posted by MalFet

Makes sense for evenly distributed alleles (.5^10 is mighty small, after all), but I've still got to think that this has the tendency to eliminate relatively less frequent traits (.9^10 isn't quite so tiny). If we did this with people, we'd run out of redheads pretty quick.
Well, the idea is obviously that genetic diversity isn't even ideal with yeast. You're taking 10 colonies of (virtually) genetically identical yeast cells. The aim is to keep the yeast the same, with minimal change. So not only is the disappearance of redheads not a problem, but you don't want them pop up, and when they do, you WANT them to be stamped out. The point is, that with good practice, the traits you want should *never* be relatively infrequent within your sample.

You can't really compare yeast with people like that, because there's an enormous, key difference - genetic diversity is completely undesirable when you're trying to maintain a pure yeast culture.
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Old 09-12-2011, 10:51 AM   #23
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Quote:
Originally Posted by emjay View Post
Well, the idea is obviously that genetic diversity isn't even ideal with yeast. You're taking 10 colonies of (virtually) genetically identical yeast cells. The aim is to keep the yeast the same, with minimal change. So not only is the disappearance of redheads not a problem, but you don't want them pop up, and when they do, you WANT them to be stamped out. The point is, that with good practice, the traits you want should *never* be relatively infrequent within your sample.

You can't really compare yeast with people like that, because there's an enormous, key difference - genetic diversity is completely undesirable when you're trying to maintain a pure yeast culture.
That's never been my understanding, based on hearing yeast people talk. Certainly some key features, particularly flocculation, are desirable in distribution.
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Old 09-28-2011, 04:41 AM   #24
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From what I've read on yeast culturing, there is no substitution to tasting some of a trial beer prior to pitching the main tank. There IS a limit to what can be done with with scoping and plating etc. This was very frustrating to me when I first started culturing. Not that I've ever noticed a problem (or done trial batches for that matter), but I was hoping for a set of rules, that if followed, would guarantee a perfect # of healthy cells that were always mostly the same yeast I bought from the lab....
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Old 12-14-2014, 03:58 AM   #25
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With 25% glycerine my vials froze solid.Is it ok?
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Old 12-15-2014, 03:25 AM   #26
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Greater than 10% glycerin leads to plasmid instability. ( plasmid instability = mutations )
10 % glycerine solution = 29.12 F degrees freezing point.
You just need to slow yeast metabolism to just under freezing.
Common misconceptions are that the colder the better.
Cryogenic temperatures can be used for gene modification on cells. Working on cells require them to stay still.
Others may know better but this is my protocols of how to keep yeast cultures dormant until needed.

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