Developmental expression and modification of genes.

Differentiating tissue is characterized by a specific repertoire of proteins out of which some are developmentally controlled. This review describes modifications in the structure of genes which encode developmentally regulated proteins. Evidence is provided for changes in chromatin conformation and DNA methylation of specific genes-either change can be observed in various stages of some vertebrates. The involvement of hormones in regulating DNA modifications is suggested, and interrelationships between DNA modifications and gene expression are discussed.