Final answer:
Covalent histone modifications can serve as binding sites for proteins that stimulate gene expression.
Step-by-step explanation:
The covalent histone modifications can serve as binding sites for proteins that stimulate gene expression. Covalent histone modifications, such as acetylation, methylation, and phosphorylation, can alter the charge and structure of histone proteins, which in turn affect the tightness of DNA winding around the histones. These modifications can create binding sites for proteins that enhance transcription by opening up chromatin regions for gene expression.