Lecture 06

Outline of Lecture 06 Patterning a Simple System I See 5 pages of notes in binder on “Introduction to Patterning” I. Overview - Much of our knowledge of A/P and D/V axis development comes from Drosophila - Proper spatial development is determined by differential gene expression - Different HOX genes are expressed along the A/P axis, and this determines fate of cells in each segment - Interestingly, order of HOX genes in genome is same order of expression II. Anterior/Posterior axis (A/P) - A/P axis is established when embryo is a syncytium - bicoid mRNA localized to anterior pole; nanos mRNA localized to posterior pole - Bicoid and nanos protein form opposing gradients along A/P axis as cells begin to form - Hunchback txn is activated by Bicoid and translation repressed by Nanos; hence, Hunchback has a graded distribution along A/P axis - Kruppel, knirps, and giant genes are have different thresholds for repression by Hunchback; hence Hb sets the anterior boundary for their expression