pattern formation

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(This is revised from the original post.)
The homeotic selector gene Antennapedia is known to specify the second thoracic segment of Drosophila melanogaster. This segment harbors a pair of legs and has no antenna or wings. In my lecture on Monday, I showed a picture of a mutant fly in which a pair of legs are sticking out form a head segment. In this form of mutant, the Antennapedia gene was expressed in the head, as well as in the thorax. So the mutant phenotype is considered as a gain-of-function phenotype, where ectopic expression of the gene in the head has caused a dominant phenotype. If the function of the Antennapedia gene is to promote the formation of the legs and to suppress the formation of antenna, what would happen in a different Antennapedia mutant where its normal expression in the thorax is lost (you could call this a recessive mutation)? Explain your answer.
-from Dr. Nakagawa

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Homeotic selector genes are necessary for the formation of distinct body segments in Dorsophila. Homeotic mutations can cause structures to be transformed into other structures. In the gain of function mutation, the mutant phenotype had Antennapedia expressed in the head (as well as the second thoracic segment) of Drosophila, causing a pair of legs to form on the head segment in place of the antennae. If a recessive mutation was seen in which the Antennapedia gene was lost in the thorax, Antennapedia would no longer have the ability to promote leg formation or suppress anntena formation in this thoracic segment. Because of this, I think that the recessive mutant phenotype would give a fly with antennae on the second thoracic segment (rather than legs).

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This page contains a single entry by mcloons published on September 26, 2011 12:05 PM.

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