Polytene chromosomes normal (Morgan, Bridges and Schultz, 1937).
Heterozygotes have ocellar bristles which are shorter and have a smaller volume than normal.
Heterozygotes have denticles that are smaller, thinner and more variable in size and shape than those in wild type. Hairs appear normal.
intermediate allele Bristles of Sb/+ less than one-half normal length and somewhat thicker than wild type. Fiber bundles in bristle shafts smaller and more numerous than in wild type; occupy a third as much of the bristle cross-sectional area in Sb as in wild type (Overton, 1967; FBrf0018805). Developmental studies by Lees and Waddington (FBrf0005804) show that trichogen is shifted to lie more or less on the level of the tormogen.
Bridges, 21st April 1923.
Associated with: l(3)89Aa1.
Insertion remains in 5 (unnamed) Sb1 revertants.
The lethality of Sb1 is probably not due to Sb, but to a second mutation on the same chromosome called l(3)89Aa1.