Geneticists have identified a number of mutations of theDrosophila gene, Dorsal. Most mutant allelesresult in dorsalized embryos, i.e. all tissues are dorsal.But one mutant allele is dominant to wild-type and results inventralized embryos, i.e. all tissues are ventral. How canthese results can be explained? Choose from answers below.
1. Mutant Dorsal cannot bind Spätzle.
2. Mutant Dorsal cannot bind Cactus.
3. The Dorsal gene is constitutively expressed in themutant.
4. Mutant Dorsal cannot bind DNA.
Mutant Dorsal initiates signal transduction in the presence orabsence of Toll.
