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Need help creating an experimental idea ASAP!

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Need help creating an experimental idea ASAP!

Postby Cerebral_Artist » Wed Nov 14, 2007 7:33 am

Alright, we're supposed to create two experiments to help prove the following. One being genetic based, and the other size-dependent adaptive based.

1. The sailfin molly, Poecilia latipinna, is an interesting freshwater fish possessing internal fertilization. In this species, males either court females or attempt forced copulations without courting. Larger males court more frequently than smaller males whereas the latter attempt more forced copulations. Variation in male size is largely determined by alleles at a single genetic locus on the Y chromosome. Describe experiments in which you could determine whether the two male behaviors represent

(i) size-dependent adaptive strategies without an underlying genetic basis (did this one already)

(ii) genetically-based alternate male reproductive strategies.


I already did part one. I can't think of any ideas for the second one (genetic based experiment). The Y chromosome controls the size of the males, so that threw away my only idea, which is to mate a small male with a large female and vice versa, to see how their offspring would react and change genetically. But the sizes would remain the same :/
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Postby mith » Wed Nov 14, 2007 7:48 am

If you want to variate genes without varying size you could try making it so big fish mate with big fish and small with small, that way it won't be size dependent unless the size dependence is measured as an absolute rather than relative.
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Postby Cerebral_Artist » Wed Nov 14, 2007 7:57 am

mith wrote:If you want to variate genes without varying size you could try making it so big fish mate with big fish and small with small, that way it won't be size dependent unless the size dependence is measured as an absolute rather than relative.


I'm sorry I don't quite understand. How would this prove that the large and small fish act the way they do due to their genetic makeup? That's the point we're supposed to convey.

Also, the size gene is only located in the Y chromosome, so why would it matter if the males mated with large or small females since the Y chromosome will carry on the genetic code for the height.

edit: I'm so confused with how to explain this, you might be right but I still don't quite get how. :(
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Postby mith » Wed Nov 14, 2007 5:03 pm

I'm assuming you have both big and small female fish. If the relative size of the male is the same as the female would it matter? Or are you measuring size as an absolute value rather than relative?
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Accepting hardships as the pathway to peace;
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