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mating with cw strains

Elizabeth Harris chlamy at ACPUB.DUKE.EDU
Thu Jul 13 08:15:16 EST 1995

re your post on bionet.chlamydomonas, one suggestion on cw mating - save a
little of your mating mixture, 0.5-1 ml or so, in a tube and leave it in
bright light overnight, then check to see if there's a zygospore pellicle
formed.  This will look like a somewhat reticulate network around the walls
of the tube, and on the surface of the liquid - try it with a wild type x
wild type cross done in parallel, so you have something to compare it to.
If you *don't* see a pellicle in your cw mating, then you have an advance
indication that you may not have gotten good mating efficiency, and you can
go ahead and repeat the cross.  This saves waiting for maturation and
visible zygotes on the plates.

In my experience, there are two types of problems with cw crosses.  First,
some of the cw strains have a high proportion of "bald" cells with no
flagella.  This is particularly true of the original Davies cw15 isolates,
in the Chlamydomonas Genetics Center collection as CC-277 and CC-278.
However, the ones we sent you are among the better ones in this respect;
CC-400 and CC-406 were selected originally for swimming and mating ability.

Second, we've had problems with crosses involving cw15 and arg7 in
combination.  In this case, mating may occur at reasonable efficiency, and
zygospores are formed, but germination and product survival are very poor.
I don't have a good workaround for this, and would be interested in hearing
the experience of others.

Elizabeth Harris
chlamy at acpub.duke.edu

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