The Drosophila Hedgehog Pathway

Question 1

What is the the Hedgehog pathway required for?

Answer 1

Segment patterning in the embryo

Question 2

What are the Hedgehog-like mutations?

Answer 2

• Hedgehog (hh)
• Smoothened (smo)
• Wingless (wg)

Question 3

What is the phenotype of hedgehog-like mutations?

Answer 3

Loss of naked cuticle

Question 4

What is the patched-like mutation?

Answer 4

• Patched (ptc)

Question 5

What is the phenotype of patched-like mutations?

Answer 5

Excess naked cuticle

Question 6

Which gene/s are required for the formation of naked cuticle?

Answer 6

hh, smo and wg

Question 7

Which gene/s suppresses the formation of naked cuticle?

Answer 7

ptc

Question 8

What did epistatic analysis of the hh/ptc mutants show?

Answer 8

hh/ptc double mutant - ptc phenotype is prevailed

Sp ptc is epistatic to hh (masks hh)

Question 9

What is expanded in ptc mutants?

Answer 9

wg

Question 10

Correct of model of hh, ptc and wg

Answer 10

hh —-| ptc —-| wg

Question 11

Which phenotype is prevalent in the hh/ptc double mutant?

Answer 11

ptc phenotype, excess of naked cuticle

Question 12

What did epistatic analysis of the ptc/smo double mutant show?

Answer 12

Has hh-like phenotype (typical of smo mutants)
wg expression not restored
smo epistatic to ptc

Question 13

If ptc/smo double mutants show a loss of naked cuticle, which is the prevalent phenotype?

Answer 13

smo

Question 14

What is the inferred pathway using the ptc/smo and hh/ptc double mutants?

Answer 14

ptc is epistatic to hh
smo is epistatic to ptc

hh —| ptc —| smo —>wg