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In a three-point testcross, it was found that the genetic map, for three, linked genes was:...

In a three-point testcross, it was found that the genetic map, for three, linked genes was: A-30 mu-B-20mu-C A genetic cross was performed and, the outcome was; that of 1000 progeny 1 double recombinant was observed. How does this compare to what we have expected? Explain this phenomenon.

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Comparing expected and given DCO, we find that expected number of DCO (60/100) is greater than the actual observed number of DCO (1/1000). This happens because of a phenomenon called as chiasma interference. ​​crossing over doesn't occur uniformly along a chromosome and formation of one chiasma also decreases the probability of another chiasma formation in immediately adjacent region of a chromosome. This lack of independence in chiasma formation and hence crossing over is known as chiasma interference. The result of this interference is the observation of fewer DCO types than that expected according to true map distances as observed in given problem.

gladiator answered 2 years ago
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