Chapter 15, Problem 27P

Summary Introduction

To analyze:

After recognition of an enhancer trap line created by P element transposition in Drosophila in which the marker gene from the enhancer trap is particularly expressed in the wing imaginal disc.

To outline the procedure used to recognize the gene contiguous to the insertion site of the enhancer trap.

To outline the procedure that reveals the expression pattern of the enhancer trap line and reveal the internal gene expression pattern of the contiguous gene.

Introduction:

Enhancer trapping is the method which allows the hijacking of an enhancer from another gene; therefore, it is useful for the identification of the enhancer. This method combines a large number of random insertion mutants with the expression of a reporter gene. The reporter gene is merged with a minimal promoter, which is insufficient to drive a detectable expression of the reporter gene used in the enhancer trapping methods. It utilizes the potential of the genomic enhancer and silencer that lie outside the construction. The expected mutation, induced by transposons, would be the insertional mutation because the additional bases are added to the original gene. The insertion of an additional base pair in the gene sequence leads to the frameshift mutation.

Therefore, the mutagenesis experiment is expected to have either gain-of-function or the loss of function mutation depending on the insertion of a base pair in the transposon. The gain of function would cause overexpression of the gene inserted adjacent to the transposons, in contrast, if it is inserted into the coding region, it would show the loss of function.