109Problemsmitosis reproduces genetically identical genotypes. Like-wise, all nuclei in every male gametophyte will be a.Inthe corn life cycle, the endosperm is formed from twofemale nuclei plus one male nucleus, so two endospermtypes will be formed as follows:/ polar3n/ sporenuclei? spermendospermAAand AaA/A/aaaand a/a/aSecond cross:a/a/3A/a?/ polar3n/ sporenuclei? spermendospermAllaAll aand aAA/a/a/a/aThe phenotypic ratio of endosperm characters wouldstill be Mendelian, even though the underlying en-dosperm genotypes are slightly different. (However,none of these problems arise in embryo characters, be-cause embryos are diploid.)b.This kind of experiment has been very useful instudying plant genetics and molecular biology. In an-swering the question, all we need to realize is that thetwo polar nuclei contributing to the endosperm are ge-netically identical. To obtain endosperms, all of whichwill be a/a/a, any a/a3a/a cross will work. To obtainendosperms, all of which will be
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This note was uploaded on 01/10/2011 for the course BIOL BIOL taught by Professor Johnson during the Spring '08 term at Aberystwyth University.