1314.4 Using the chi-square test in linkage analysissome blocks of two. Some data from an actual cross ofA±aare shown in the table below.OctadsAaAaAaAaAaAaaAaAAaAaAAaaAAaaAaAaAAa1261329111012Total²300aAAaAaThe ﬁrst two columns are from meioses with nocrossover in the region between the Alocus and thecentromere. These are called ﬁrst-division segregationpatterns (MIpatterns)because the two different allelessegregate into the two daughter nuclei at the ﬁrst divi-sion of meiosis. The other four patterns are all frommeiocytes witha crossover. These patterns are called second-division segregation patterns (MII)because, as aresult of crossover in the centromere-to-locus region, theAand aalleles are still together in the nuclei at the endof the ﬁrst division of meiosis (Figure 4-15). There hasbeen no ﬁrst division segregation. However, the secondmeiotic division does move the Aand aalleles into sepa-rate nuclei. Figure 4-15 shows how one of these M
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