Transformation of ray 6 to a thin ray which is anteriorly displaced and fuses with ray 4 (95%). A 10th ray is found in about 50% of the sides scored. Slightly shorter than WT. mab-21(bx53)/yDf10 is embryonically lethal with embryo arrest at 2 fold stage.

Heterozygotes are WT and segregate WT, Dpy Steriles and dead eggs. Derived from strain TY1353. Grows fairly slowly but seems more stable than TY1353, which gives lots of steriles.

Heterozygotes are Unc-93 and segregate more Unc-93, yDf10 homozygotes (dead eggs) and Unc-93 Dpy-17 homozygotes (young dpy-17 larvae are easily recognizable as abnormal spindle-shaped things). Difficult to maintain and use. yDf10 apparently causes semi-sterility (a second strain constructed by the Mark Edgley at the CGC, yDf10/qC1, exhibits same sterility), and unc-93 is Egl and difficult to mate into. Some Df homozygotes are laid, but most remain inside the mother.