Example 2
Left = wild type male
Right = Tab 1+ heterozygous male
Tab = transabdominal mutation
sr = striped
Abd-B = abdominal-B gene
This mutation causes part of the thorax to develop as tissue usually found in the 6th abdominal segment (A6)
This occurs through a chromosomal inversion where one of the breakpoints is within an enhancer region of the sr gene which induces gene expression in certain areas of the thorax.
The other breakpoint is near a transcription unit of the Abd-B gene which encodes a transcription factor normally found in the A6 region. This gene gives an abdominal phenotype on any tissues in which it is expressed.
In the Tab inversion the sr enhancers are put next to the Abd-B transcription unit causing the Abd-B gene to be activated in part of the thorax where sr would normally be expressed.
