THE CYTOGENETIC LOCALIZATION OF THE ALCOHOL DEHYDROGENASE-1 LOCUS IN MAIZE

The alcohol dehydrogenase-I (Adh) locus in maize has been positioned relative to thirteen reciprocal translocations that have breakpoints in the long arm of chromosome I (1L). The methods of GOPINATH and BURNHAM (1956) to produce interstitial segmental trisomy with overlapping translocations and of RAKHA and ROBERTSON (1970) to produce compound B-A translocations were coupled with the co-dominant nature of the ADH isozymes to allow the cytological placement. The results of several crosses are consistent with Adh being in the region of 0.80-0.90 of 1L.—The duplication that results from the overlap of translocations 1-3 (5267) and 2-3 (5242) and that includes Adh was studied with respect to meiotic segregation and pollen transmission. When heterozygous with normal chromosomes, a low level of recombination within the duplicated regions is detectable and the duplication and normals are recovered with equal frequencies through the female. In the pollen, the hyperploid grains cannot compete equally with the euploids in achieving fertilization.—The use of co-dominant heteromultimeric isozymes as genetic markers for the development of a series of interstitial segmental trisomics in maize is discussed.