The One Band-One Gene Hypothesis: Evidence from a Cytogenetic Analysis of Mutant and Nonmutant Rearrangement Breakpoints in Drosophila Melanogaster (original) (raw)

1. George Lefevre, Jr.
2. Department of Biology, California State University, Northridge, California 91324

Excerpt

Fundamental questions relating to the organization of eukaryotic chromosomes have been profitably attacked by recent cytogenetic investigations on polytene chromosomes of Drosophila melanogaster. For example, Judd et al. (1972) have demonstrated that in the zeste-white (z–w) interval, only one genetic function is associated with each visible band or chromomere. Other studies have shown that the centric “heterochromatin” (in which repetitive DNA is concentrated) is not polytenized (Rudkin, 1969; Gall et al., 1971). Further, the amount of crossing-over between two cytologically localized genes has been correlated with the quality of the bands, i.e., their DNA content, not simply with the number of bands in the interval (Lefevre, 1971). The early suggestion of Bridges (1935) that “repeat” band patterns signify duplicated genetic content has been supported for the region containing the roughest (rst) and vertical (vt) loci (Lefevre and Green, 1972). These and other cytogenetic studies apply to the way the visible...