A chromosome substitution analysis of geotactic maze behavior in Drosophila melanogaster.

Positive and negative geotactic maze behaviors were selected in strains of Drosophila melanogaster, for over 40 generations on 15-unit classification mazes. A chromosome substition analysis of these behaviors was undertaken to determine which of the three major chromosomes is most important in causing the differences in geotactic maze behavior between the divergent strains. By following the appropriate mating scheme, every possible homozygous chromosomal combination of the X, II, and III chromosomes from the geopositive and geonegative strain was produced. Heterozygous combinations were also produced to test for dominance and interchromosomal interactions. The results indicate that all three chromosomes are involved in geotactic behavior. The order of importance was II greater than III greater than X. Dominance effects were found in females of the X chromosome from the geopositive strain and for the III chromosome from the geonegative strain. No evidence for interchromosomal interactions was uncovered.