Department of Animal Ecology, Ecology Building, Lund University, SE-22362 Lund, Sweden.
Trends Genet. 2010 Jan;26(1):15-20. doi: 10.1016/j.tig.2009.11.006. Epub 2009 Dec 4.
Recent studies have demonstrated an extensive male bias in the gene expression on Z chromosomes in species with a ZW sex determination (e.g. birds), suggesting that ZW females have incomplete dosage compensation. We propose that the extensive male bias on Z chromosomes is caused by the functional properties of male-adapted genes, which make them unsuitable for high expression in females, and that ZW females are dosage-compensated to a point where they have achieved enough compensation to maintain the integrity of critical networks. In ZW systems, Z chromosomes spend two-thirds of their evolutionary time in males, and pronounced sexual selection in males and the male mutation bias can interact and affect levels of sexual antagonism, causing more extensive male bias in gene expression on Z-linked genes. These patterns and processes contrast with those acting on genes on the X chromosome in XY species, and might help explain the discrepancies in the degree of sex-biased gene expression and dosage compensation in XY and ZW systems.
最近的研究表明，在具有 ZW 性别决定的物种（如鸟类）中，Z 染色体上的基因表达存在广泛的雄性偏倚，这表明 ZW 雌性存在不完全的剂量补偿。我们提出，Z 染色体上广泛的雄性偏倚是由适应雄性的基因的功能特性引起的，这些特性使它们不适合在雌性中高表达，而 ZW 雌性则进行了剂量补偿，达到了足以维持关键网络完整性的程度。在 ZW 系统中，Z 染色体在雄性中花费了三分之二的进化时间，雄性中的明显性选择和雄性突变偏向可以相互作用并影响性拮抗的水平，从而导致 Z 连锁基因上的基因表达中出现更广泛的雄性偏倚。这些模式和过程与 XY 物种中 X 染色体上的基因作用相反，这可能有助于解释 XY 和 ZW 系统中性别偏向基因表达和剂量补偿程度的差异。
