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Name: Deven Mistry
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This is genetics question: I would like to know how someone can come up with a recombinance map using map units for a trihybrid testcross? (Sorry I do not have any more info on the question.)

By doing a trihybrid testcross and looking at the number of offspring with expected gene combinations versus the number with unexpected gene combinations, one can calculate the map unit distance between those genes. These map units do not represent actual distances on chromosomes, but rather show how frequently crossing over might occur during meiosis. The reasoning is that the closer two genes are on a chromosome, the less likely they are to be separated during crossing over. Since all three genes in your trihybrid are presumably on the same chromosome, they should stay together in the offspring, except where crossing over occurs. Does that make sense, or do you need more background?

Ellen Mayo

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