The localization patterns of Numb and Insc are shown with blue or red crescents,
respectively. The size of the progeny reflects the asymmetric/symmetric-sized
division patterns induced by the Numb crescent. Dashed line on the GMCs
represents the axis of cell division. The early distribution of Numb is punctate
throughout the cortex of GMC-1, perhaps allowing for restricted Notch signaling.
In Wild type (A), before cytokinesis, Notch activity localizes Insc and Numb to
opposite locations in an axis perpendicular to the plane of cytokinesis. As a
consequence the smaller apical daughter cell accumulates Insc and is specified
as ‘sib’ via Notch activity; the basal daughter cell, inherits
Numb, which specifies the RP2 fate by inhibiting Notch activity. In
Notch mutant embryos from early (B) and late shifts (C),
both daughter cells are specified as RP2. Asymmetrical cytokinesis in C is due
to earlier Notch activity in GMC-1 that allows partial localization of
Insc/Numb.