grh^B37/grh³⁷⁰ mutants do not have surviving doublesex-expressing larval terminal neuroblasts in the terminal region of the female third instar larval ventral nerve cord, similar to controls.

At 96 hours, 65% of grh³⁷⁰ type I neuroblasts are smaller than normal.

In grh³⁷⁰/Df(2R)Pcl7B larvae have 1-2 extra ventral clusters of post-embryonic neuroblasts per hemisegment in the abdomen and the clusters themselves have more cells. In contrast, there are less post-embryonic neuroblasts in the thoracic segments of these larvae. This is reflected at mid-third instar by an increase in mitotic cells per neuroblast cluster in the abdomen and a decrease in mitotic cells per neuroblast cluster in the thorax.

Neural proliferation is reduced in the thorax of grh³⁷⁰/Df(2R)Pcl7B mid-L3 larvae with each neuroblast lineage reduced from an average of 7.1 cells in wild-type larvae incorporating BrdU during the 72-78 hours to 5.3 cells in grh³⁷⁰/Df(2R)Pcl7B mutants. In contrast, neural proliferation in the central abdomen is increased with cells still dividing in grh³⁷⁰/Df(2R)Pcl7B abdomens after the 72-hour time point when division has stopped and apoptosis has occurred in wild type. grh³⁷⁰/Df(2R)Pcl7B ventromedial and ventrolateral neuroblast lineages show a 3.5-fold increase in size compared to the wild-type average. These mutants also generate some supernumerary postembryonic lineages that occupy ectopic positions, often close to the midline.

Homozygous animals survive beyond embryogenesis. Most hemizygotes die during the third larval instar stage, some survive to pupation and 1-2% eclose as adults which have persistently shaking appendages and die shortly after eclosion.

Lethality acts in the larval/pupal stages, with a few escapers.

Virtually identical to grh^IM in phenotype: degenerating head skeleton. Cuticle susceptible to rupture.