Axis Formation Flashcards
Name some regulatory circuits
Changes in gene expression respond to external signals TFs regulate other TFs and downstream proteins eg. Morphogens
Feedback loops stabilise expression (after initial expression is turned on by a transient signal- remembered by all cell descendants)
One signal can coordinate expression of several genes eg. Glucocorticoid hormone+receptor binds to other transcription factors at gene promotors to get high levels of transcription
Feedback in a pathway eg. Myogenesis- signal➡️ MyoD, myogenin, Myf5, Mrf4➡️ Mef2➡️ muscle structural genes➡️ muscle development
Mrf4 and Mef2 feedback to themselves Myf5 and myogenin
How do drosophila establish their axis?
Mother deposits mRNA➡️morphogen at one end which becomes the anterior/head of the fly
The concentration gradient affects he cell fate via paracrine signalling
How are hox genes unusual?
They cluster with many related genes in large, highly conserved domains and their gene expression is co-linear ie. The position in the genome relates to position in the organism
What is the significance of retinoic acid?
It is an external signal that turns Hox genes on
Binds to proteins (RXR, RAR) on the Retinoic Acid Response Element (RARE)
Acts to simultaneously activate and repress many genes (eg. Pluripotency genes)
How are genes regulated?
By a committee of regulatory proteins- each will have an activating or inhibiting effect that influence the probability of initiating transcription
