染色体组织在演化上基本上是稳定的。在果蝇中，超过95%的基因仍然保留在距今大约6300万年前分化的12个物种中的同一染色体臂上。然而，对Y染色体所做的一项研究显示，黑腹果蝇与Y染色体相关的基因中只有1/4在其他11个所测序的物种中也与Y染色体相关。与以退化及基因丢失为特征的哺乳动物Y染色体形成对比的是，果蝇Y染色体上的基因增加与基因丢失相比超过10比1。（生物谷Bioon.com）
生物谷推荐原始出处：
Nature 456, 949-951 (18 December 2008) | doi:10.1038/nature07463
Low conservation of gene content in the Drosophila Y chromosome
Leonardo B. Koerich1, Xiaoyun Wang2, Andrew G. Clark2 & Antonio Bernardo Carvalho1
1 Departamento de Genética, Universidade Federal do Rio de Janeiro, Caixa Postal 68011, CEP 21944-970, Rio de Janeiro, Brazil
2 Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853, USA
Chromosomal organization is sufficiently evolutionarily stable that large syntenic blocks of genes can be recognized even between species as distantly related as mammals and puffer fish (450 million years (Myr) of divergence)1, 2, 3, 4, 5, 6, 7. In Diptera, the gene content of the X chromosome and the autosomes is well conserved: in Drosophila more than 95% of the genes have remained on the same chromosome arm in the 12 sequenced species (63 Myr of divergence, traversing 400 Myr of evolution)2, 4, 6, and the same linkage groups are clearly recognizable in mosquito genomes (260 Myr of divergence)3, 5, 7. Here we investigate the conservation of Y-linked gene content among the 12 sequenced Drosophila species. We found that only a quarter of the Drosophila melanogaster Y-linked genes (3 out of 12) are Y-linked in all sequenced species, and that most of them (7 out of 12) were acquired less than 63 Myr ago. Hence, whereas the organization of other Drosophila chromosomes traces back to the common ancestor with mosquitoes, the gene content of the D. melanogaster Y chromosome is much younger. Gene losses are known to have an important role in the evolution of Y chromosomes8, 9, 10, and we indeed found two such cases. However, the rate of gene gain in the Drosophila Y chromosomes investigated is 10.9 times higher than the rate of gene loss (95% confidence interval: 2.3–52.5), indicating a clear tendency of the Y chromosomes to increase in gene content. In contrast with the mammalian Y chromosome, gene gains have a prominent role in the evolution of the Drosophila Y chromosome.
