5.4 Families of transcription factors. There are several families of transcription factors grouped together by their structural similarities and their mechanisms of action. Homeodomain transcription factors are important in specifying anterior-posterior axes, and hormone receptors mediate the effects of hormones to the genes. 5.5 Histone acetylation. Histone acetylation is a critical step in clearing the way for the transcription initiation complex.
Derepressed chromatin is characterized by acetylated histones.
5.6 Enhancers and cancers. Enhancer trapping may occur accidentally during development and place a new gene next to a particular regulatory element. When growth factor genes are placed next to the genes involved in making antibodies, the results are leukemias. 5.7 The FLP-out technique. It is often the case that one wants to determine what a gene product does when it is expressed in a cell type that does not usually express that gene.