INTRAGENIC RECOMBINATION IN MAIZE: POLLEN ANALYSIS METHODS AND THE EFFECT OF PARENTAL Adh1⁺ ISOALLELES

Michael Freeling ¹

¹ Department of Genetics, University of California, Berkeley, California 94720

The ability to stain mature pollen grains for the presence of alcohol dehydrogenase (ADH) activity permits the quantitation of ADH ⁺ gametophytes at frequencies below 10^-6. This resolution allows reversion and genetic fine structure analyses. The rationale of pollen analysis follows Nelson's prototype studies with waxy. As with the waxy gene, revertant frequencies for seven Adh1-deficient ( Adh1^-) alleles appear to be in excess of microbially derived expectations. Each of the seven Adh1^- alleles were derived from one of three naturally occurring isoalleles. Based on Schwartz's protein level characterizations of the mutants' products, it was anticipated that the seven Adh1^- alleles should recombine to yield ADH⁺ cistrons in certain pairwise combinations. This expectation was not met. The parental "wild-type" isoalleles from which the mutants were derived appear to be structurally divergent. The discussion interprets these data in view of understanding naturally occurring cistronic variation.

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