We have determined the nucleotide sequences of zein cDNA clones ZG14, ZG15, and ZG35. The three clones have 95 to 98% homology to the previously published sequence of clone A20, and 84% homology to sequences of the zein subfamily A30. Comparison of all sequences of the A30 and A20 subfamilies highlights the following features: the 5′ nontranslated regions are 68 and 57 nucleotides in length for the A20- and A30-like mRNAs, respectively, and contain at least three repeats of the consensus sequence ACGAACAAta gG; the majority of these genes are highly clustered as judged from pulsed-field gel electrophoresis of high molecular weight maize DNA. Furthermore, we discuss a model for the evolution of the multigene family which stresses the special importance of unequal crossing-over and gene conversion in this system.
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