Yeast Reproduction Question

I was driving to work thinking today about how yeast reproduces. Is it sexual or asexual reproduction. I ask because I have been wondering about 'custom straining' or something, say I have a yeast that I like the beer it produces but it can't handle high ABV solutions. Can I put a packet of 'flavor' yeast and a packet of 'sturdy' yeast and expext them to produce unique offspring? Or do yeast just replicate themselves and I would end up with a collection of flavor and sturdy yeast comingled without cross breeding?

-dylan.

Yeast reproduce by splitting from one yeast cell into two yeast cells, so no unique offspring, you would have a lot of stressed out yeast, due to both strains trying to take over the beer.

Reproduction is almost entirely asexual. I'm told that under certain high stress situations, they can reproduce sexually, but I doubt we're running into those situations.

Yeast can reproduce sexually, but only if they're haploid (have a single set of chromosomes). Commercial yeast products are almost 100% diploid, or sometimes even higher polyploids. In order to get a significant amount of sexual reproduction, you'd need to force the cells to undergo meiosis, which basically means putting them under significant stress for multiple generations - very high temperatures, very high-gravity wort, etc. Obviously that wouldn't make very good beer though.

For the most part, what's going to happen when you mix two strains is that one will reproduce faster than the other, even if only slightly, and end up dominant. There was an article about it BYO a few months ago.