5-350 Lecture : Patterning a Simple System

• School: University of Windsor
• Department: Biological Sciences
• Course: 5-350
• Professor: Asish Mukhopadhyay

Document Summary

Patterning a simple system determined = cells cannot alter their anterior/posterior identity early in development (though they can alter proximal distal identity) Hox genes - determine mammalian anterior/posterior fate located on chromosome in same order as they are expressed. Hox homeotic genes - determine drosophila anterior/posterior fate similar to hox genes. Unfertilized drosophila egg: maternal expression bicoid - mrna expressed at head nanos - mrna expressed at tail homeotic bicoid nanos. **both code for morphogens: substances present in a gradient specify different cell fates at different concentrations** morphogen. Early drosophila embryo is a syncitium before cellularization (when cells reform), gradients form syncitium bicoid expression leads to hunchback protein txn/expression a threshold of bicoid is needed to activate hb txn. Hb nanos codes for a transcriptional repressor no nanos --> hb is expressed throughout entire embryo. **bicoid and nanos create a gradient of hb (which is itself a tf)**