Constitutive heterochromatin represents a significant portion of eukaryotic genomes, but its functions still need to be elucidated. Even in the most updated genetics and molecular biology textbooks, constitutive heterochromatin is portrayed mainly as the ‘silent’ component of eukaryotic genomes. However, there may be more complexity to the relationship between heterochromatin and gene expression. In the fruit fly Drosophila melanogaster, a model for heterochromatin studies, about one-third of the genome is heterochromatic and is concentrated in the centric, pericentric, and telomeric regions of the chromosomes. Recent findings indicate that hundreds of D. melanogaster genes can ‘live and work’ properly within constitutive heterochromatin. The genomic size of these genes is generally larger than that of euchromatic genes and together they account for a significant fraction of the entire constitutive heterochromatin. Thus, this peculiar genome component in spite its ability to induce silencing, has in fact the means for being quite dynamic. A major scope of this review is to revisit the ‘dogma of silent heterochromatin’.

组成型异染色质代表了真核生物基因组的重要部分，但其功能仍需要阐明。即使在最新的遗传学和分子生物学教科书中，组成型异染色质也被主要描绘成真核基因组的“沉默”成分。但是，异染色质和基因表达之间的关系可能更加复杂。在果蝇果蝇（Drosophila melanogaster）中，它是异染色质研究的模型，大约三分之一的基因组是异色的，并且集中在染色体的中心，近中心和端粒区域。最近的发现表明，数百个D. melanogaster基因可以在组成型异染色质中适当地“生活和工作”。这些基因的基因组大小通常大于常染色体基因，并且它们一起占整个组成型异染色质的很大一部分。因此，尽管该独特的基因组成分具有诱导沉默的能力，但实际上具有相当动态的手段。这篇综述的主要范围是重新审视“沉默异染色质的教条”。