Outline

4.1 The Fruit Fly Retina Develops through an Orderly Progression of Gene Expression and Signaling

• BOX 4.1 TRANSGENICS, KNOCKOUTS, AND KNOCKINS

4.2 Several Factors Influence Whether a Cell Will Become a Neuron or a Glia

4.3 The Molecular Differentiation of Motor Neurons Is Orderly

4.4 Neural Crest Cells Are Affected by Their Migration and Destination

• RESEARCHERS AT WORK Neural Crest Cells Adopt New Fates after Transplantation

4.5 The Neurotransmitter Phenotypes of Autonomic Neurons Are Guided by Their Targets

• RESEARCHERS AT WORK Targets Can Regulate the Neurotransmitter Phenotype of Afferents

4.6 The Fate of a Cortical Neuron Is Influenced Both Before and After Migration

• RESEARCHERS AT WORK Cortical Neuron Fate Is Specified after the S Phase

4.7 Later Events in Development Are More Evolutionarily Labile