Note that a new picture has been posted on this page. If you have already read this page, scroll down; otherwise read on.
The charts that follow have to do with one specific case, but obviously can be used for any similar circumstance, which is the pairing of any animal or plant of a pure strain of a dominant characteristic with an individual of a pure recessive characteristic. The pure dominant is known as [ D D ], which indicates that that individual has inherited that dominant characteristic from both of its parents; and also indicates that when gametes are formed, each containing half of that individual's DNA, they all will have that dominant "gene" (or "DNA sequence" if you will). The pure recessive is designated [ r r ], which indicates the same assumptions with regard to that individual's inheritance and gametes.
Specifically, in this case we are talking about crayfish, Procambarus alleni, who are native to peninsular Florida in fresh water. The male is from the wild, and although it is not the most typical example, it is not from a terribly rare breed either. It only differs from the "most typical" of its species in that it has some blue. Pictures of it are found on the Florida crayfish mating page. The female is a young female of the white mutation:
| And here is where I go out on a limb. I am designating this individual [ r r ], for no particularly good reason except that it is a departure from what one would "normally" expect, and such characteristics often are recessive. Whether I really am out on a limb or not is to be discovered. Read on. |
And here is what just happened on the 6th of May:
(What follows is on a white background because it is actually a graphic - since I wanted to make charts "one the fly" while typing text, I did the whole thing as a bitmap in the Windows Paint program.) (And note that at the time this page was first written, what follows was purely speculative - that is, I did not at that time have any very good reason to think that the first pairing would even occur. Not all female crayfish will find every male acceptable. But as we see in the above photograph, we now have some reason to think that the children described below might actually be born.)
Not only that, but if you look up the page alongside the picture of the female, you'll notice that I covered my *** by saying that I had designated her as a double recessive "for no particularly good reason"; and I state that I could be out on a limb. Okay, If I am indeed out on a limb then the very first pairing, of the "wild blue" male to the "pure" white female, might show results markedly different from what I have described. For one thing, maybe that white is not recessive at all, and is a dominant albinism. If that is the case, then it becomes a matter of "relative dominance" - at one extreme, all the offspring would be
"wild type", in which case we don't know whether we are dealing with a dominant-recessive combination or simply a "more dominant"-"less dominant" combination; at the other extreme, all the offspring are white, in which case we are presented with the same in reverse. We would not know very much at that point, but we still could go on, designing the rest of the experiment so as to choose the pairings that will give us the most definitive answers to the question.
[ Let's not get into a "conflict of interest" here. In one room we shall breed white to white, expecting to get all white offspring, for the marketplace. But in the room where the experiment is going on, let us not choose mates on that basis, but instead let us make the pairings that will give us the most information, even to the extent of thinking the way a chess-player does: "If I choose a given pair now, what experimental pairing will that allow me to make in the next generation, avoiding ambiguity to the greatest possible extent". ]
Well, it makes little sense to be speculating that far ahead just now, when we haven't even seen the result of the first pairing yet; but it does make sense to be aware now that one or two generations are probably not going to settle the question(s).
Back to that "conflict of interest" question for just a moment. This research may serve a purely scientific purpose on the one hand (satisfying my personal curiosity to some extent, if nothing more); but there is the other level: Perhaps I wind up with a good true-breeding strain of pure white who are provably descended from an "outcross". I think any breeder would agree that that is a desirable outcome to the project, satisfying both the "curiosity" level and the level of "profit motive"... (I guess the "pure scientists" will have me taken out and shot after the revolution, but oh, well).
Update May 10, 2007: The "wild" male and the white female having mated, presumably she is pregnant, so in a few weeks we might be able to know a little bit about the first (or second, really) of the above charts.
I am on Yahoo Messenger, my handle is smithroney and you can click on my name and then in the Contacts menu read my profile. Message me or send me email at [email protected]; or if you use a mail program, click here.
learn Spanish
other stuff
Home
Florida Crayfish mating
Blondie - an unusual crayfish