Expression of PoxmScer\UAS.cJa under the control of Scer\GAL4how-24B results in a severely altered muscle pattern in the embryo, which varies among different segments and embryos. The most striking defects are seen in the dorsal and dorsolateral muscles. Ectopic muscles are generated in most segments in the dorsal region. Ectopic muscles similar in shape and orientation to muscle DA3 are found in the dorsolateral region, which is largely free of muscles in wild-type embryos. Several muscles of abnormal shape are generally seen at the position where muscle DA1 is normally found. Muscles LL1, DO4 and DO5 have aberrant shapes or are missing in some segments. Some of the lateral muscles are abnormally shaped. The ventral muscles remain largely unaffected, although some muscle fibres appear enlarged.
Expression of PoxmScer\UAS.cJa under the control of Scer\GAL4how-24B affects the number of adult muscle precursors in stage 14 embryos; in the lateral mesoderm, in most segments the dorsolateral DLaPs are missing and only one of the two lateral LaPs is present. In the dorsal region, two dorsal DaPs instead of one are present in approximately half of the segments. In the ventral region, the number of ventral VaPs is unaffected.
Pharate adults expressing PoxmScer\UAS.cJa under the control of Scer\GAL4ey.PH show a headless phenotype. Three classes of phenotype are seen; class I pharate adults lack all head structures derived from the eye-antennal discs, class II consists of eyeless flies which lack most head structures and both antennae and class III consists of eyeless animals with large parts of the head missing but one or both antennae present.