ALLELIC VARIATION AT THE LEVEL OF INTRAGENIC RECOMBINATION

Michael Freeling ¹

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

This report examines five different naturally occurring alcohol dehydrogenase-1 alleles via the recombinational behavior of Adh1^- mutants induced within them. Twenty-two biochemically characterized Adh1^- mutants have been assessed for ability to recombine intragenically, using data generated by specifically staining for the presence of ADH in pollen grains. Each of the five naturally occurring Adh1 progenitor isoalleles appears unique. Allelic variation exists in (1) the rate of intragenic recombination sustained by an allele, and (2) the pattern of recombinational success or failure based on the ancestry of each mutant in a heteroallelic pair. In other words, we find quantitative and qualitative Adh1 allelic variation at the level of intragenic recombination. I have experimentally excluded several explanations for recombinational restriction. These results will be related to the structure, function and naturally occurring variability of the gene in higher organisms. Specifically, the "recon" (unit of recombination) has been resurrected as a potentially useful unit of natural selection. The reasonableness of several genres of hypotheses in evolutionary/population genetics, particularly those involving linkage disequilibrium, is called into question.

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