PLEASE POST HERE ALL YOUR QUESTIONS REGARDING DEVELOPMENT. A FEW NOTES FOLLOW....(they're just some quick notes that I made some time ago, and do not replace, by any means, your class notes or the textbook, or any other course materials!)
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2 comments:
for your example in gap genes, can you explain how the product of each gap gene inhibit other gap genes but particular combination of gap gene product switch on expression of pair rule genes?
Thank you
Yes. One way you can think of it is: each gap and pair-rule gene is controlled by enhancers and silencers, and these enhancers and silencers, in order 'to work' , have to be bound by particular trans-regulattory factors.
The protein products of gap genes are proteins that, directly or indirectly, act as trans-regulatory factors for pair-rule as well as gap genes (among others).
These proteins act as 'positive regulators' of pair-rule genes and as 'negative regulators' of other gap genes.
So, if you have a lot of one gap protein in one nucleus, there will be strong repression of the other gap genes in that nucleus.
Maternal effect gene products also act on the expression of gap genes.
So, each nucleus will end up 'containing' a particular mix of gap proteins. Depending on which proteins are in the mix, and in what proportions/amounts, it will activate the expression of certain pair rule genes, but not others. Kind of like the practice question with the 4 transcription factors...regions that have a particular combination of TFs will express our gene X.
I hope this helps.
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