The recombinational analysis of aberrations and the position of the notch locus on the polytene chromosome of Drosophila.

The recombinational analysis of heterozygotes for a point-mutant N and a deficiency N suggests that the map region approximated by the interval fa to nd2 is at the right edge of salivary band 3C7 or in the interband to the right. The map region N55ell to fa can be anywhere between the left-interband and the right edge of 3C7. We discovered that small inversions also can be used in the recombinational analysis, and the inversion data support the conclusions already described. The reactivation of latent mutability in a Notch inversion resulted in reinversion of the original aberration, followed by reversion of N to N+. From the same Notch inversion, we isolated a spontaneous deficiency superimposed upon the original aberration, which supported our hypothesis that two of our w to N deficiencies probably originated as deficiencies superimposed upon inversions.