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Lecture 18

Lecture 18- Extensions of Mendelian Genetics II

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Human Biology
Christian Campbell

Thursday, March 12, 2009 - Lets take stock. Here is where we started this term: Mendels simple traits, the antagonistic pairs we saw it was a useful way to explain simple patterns of inheritance. What we saw in last lecture is that this is inadequate in explaining variation we find in the world around us. The variation in the world around us is more complex and therefore, means that somehow we have to alter our understanding, make wrinkles in Mendels laws so it better accommodates the natural variation that is obvious in terms of allelic diversity and patterns of inheritance we see in the world around us and we touched on those in the last lecture. - This is where we re at to day, co nt in uin g wi th the co nc ept that there are wrinkles in Mendels laws to help the variation in genetics in the world we see around us. - We hear about allelic variation in the world around us all the time. - This is a story in Nature News an d CB C news an d pu bl ished in Cur rent Biology last year in 2008. It is an interesting story about blind cave fish and how it is they do or do not perceive light in their environment. - The fish in question is an Astyanax mexicanus. As the name implies it is a blind cave fish from Mexico. It turns out there are many caves throughout the Mexican desert where the blind cave fish reside. - Scient ists workin g on these bl in d cave fish de cided to do an interest in g experiment. What they did was to take fish they found from these cave as well as sub-species they found on the surface and they did what all organisms like to do: they made them have sex and produce offspring. - So what did they find when they did this? First he wants us to note that the blind fish in the slides have no pigment in its eyes whatsoever and in the fry from the surface subspecies, you can find perfect eyes, those nice black eyes. They took fish from cave one and crossed fish from cave one with them and what they found was that all of the offspring F1 were blind. By contrast, if they took cave 1 and crossed them with fish from cave 2 so different locations in the desert, what they found were that the F1 could see. - This suggests something to us since they were able to show time and time again with a number of cave comparisons so there is his final one in the slide, that is, cave 1 with cave 3 fish, both blind, the offspring however can see.
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