How I love teaching about body plan development and the genetic basis of developmental biology! Fly embryos are really amazing little things (if only I could have gotten past my innate repulsion toward fruit flies, I would have been a fruit fly developmental biologist in a heartbeat…thank goodness for zebrafish). Last week in lab, my students and I examined fruit fly embryos and larvae and discussed the genetic basis of development (see below and the image). Stay tuned for another exciting picture about gene regulatory elements and the power of transgenic approaches.
This example of how one pair rule gene (hairy) can influence the expression of another pair rule (fushi tarazu, ftz) is classic. The fly embryo at the bottom of this image is mutant for the hairy gene. All of the embryos carry the ftz:LacZ transgenic reporter, making it easy for us to detect where ftz is expressed. The three embryos at the top show the normal pattern of ftz stripes (which roughly correspond to the future segments of the fly body). What is the relationship between hairy and ftz? What would you do to confirm this type of genetic interaction?
Often we think of transcription factors as positively regulating gene expression of their targets, but transcription factors are just as likely to repress gene expression as to activate it. And just because a gene product activates or represses a particular gene, doesn’t mean that it’s a transcription factor. How can we distinguish between transcriptional control and other forms of gene regulation?