Many of these sequences regulate the structure of chromosomes by limiting the regions of heterochromatin formation and regulating structural features of the chromosomes, such as the telomeres and centromeres. Other noncoding regions serve as origins of DNA replication. Finally several regions are transcribed into functional noncoding RNA that regulate the expression of protein-coding genes (for example ), mRNA translation and stability (see miRNA), chromatin structure (including histone modifications, for example ), DNA methylation (for example ), DNA recombination (for example ), and cross-regulate other noncoding RNAs (for example ). It is also likely that many transcribed noncoding regions do not serve any role and that this transcription is the product of non-specific RNA Polymerase activity.