The following are examples of how eukaryotic cells may control gene expression: small RNA molecules, methylation of DNA and histones, histone acetylation, promoter region that controls the initiation of transcription, enhancer regions which are frequently found very far away from the promoter region, alternative splicing of mRNA, RNA binding proteins, 5' cap, and 3' poly-A tail on mRNA to improve stability and reduce likelihood of degradation, and inducible and repressible operons.