140Chapter 4 •Eukaryote Chromosome Mapping by Recombination1000 linear asci are isolated and categorized as in theabove table. Map the adand nicloci in relation tocentromeres and to each other.SolutionWhat principles can we draw on to solve this problem?It is a good idea to begin by doing something straightfor-ward, which is to calculate the two locus-to-centromeredistances. We do not know if the adand the nicloci arelinked, but we do not need to know. The frequencies ofthe MIIpatterns for each locus give the distance from lo-cus to centromere. (We can worry about whether it isthe same centromere later.)Remember that an MIIpattern is any pattern that isnot two blocks of four. Let’s start with the distance be-tween the niclocus and the centromere. All we have todo is add the ascus types 4, 5, 6, and 7, because they areall MIIpatterns for the niclocus. The total is 5±90±1±5²101 out of 1000, or 10.1 percent. In this chap-ter, we have seen that to convert this percentage intomap units, we must divide by 2, which gives 5.05 m.u.
This is the end of the preview. Sign up
access the rest of the document.