The Notch locus of Drosophila melanogaster.

The Notch locus appears to correspond to a 37 kb transcription unit. Homologous poly(A)+ RNA is about 11.7 kb. Nine RNA coding regions have been detected and localized within the transcription unit by S1 nuclease analyses. These range in size from 130 to 7250 bp. Sequences within the 3' coding region are variably used. Twenty-four Notch locus "point" mutations have been examined. Seven are associated with DNA insertions. Four insertions are associated with dominant mutations and are located within or very near RNA coding sequences of the 37 kb transcription unit. Three insertions are associated with recessive mutations and fall within intervening sequences. The positions of all insertions agree with the genetic map. It is estimated that, in the Notch region, one map unit corresponds to approximately 275 kb. On this basis, most of the 17 mutations that were not associated with DNA insertions can be placed within coding sequences of the 37 kb transcription unit.