If you overexpress various Hedgehog constructs (panel A) in normal fly embryos and examine the pattern of Wnt expression (a well characterized target of Hedgehog signaling), you observe a striped pattern of expression in all cases, but some constructs lead to thicker stripes than normal (panel B).
a. Which part of the Hedgehog molecule is responsible for signaling (1 point)? Explain your answer (2 points, 1-2 sentences).
b. All the cells in the embryo are overexpressing the various Hedgehog constructs. Why is it, do you suppose, that you observe the same basic striped pattern of Wnt expression in all of them (2 points, 1-2 sentences)?
c. Why do you see stripes of Wnt expression even in the absence of Hedgehog overexpression (1 point, 1-2 sentences)?