染色體組織在演化上基本上是穩(wěn)定的,。在果蠅中,，超過95%的基因仍然保留在距今大約6300萬年前分化的12個物種中的同一染色體臂上。然而,，對Y染色體所做的一項研究顯示,，黑腹果蠅與Y染色體相關(guān)的基因中只有1/4在其他11個所測序的物種中也與Y染色體相關(guān)。與以退化及基因丟失為特征的哺乳動物Y染色體形成對比的是，果蠅Y染色體上的基因增加與基因丟失相比超過10比1,。（生物谷Bioon.com）
生物谷推薦原始出處：
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.
