Dosage compensation is less effective in birds than in mammals.
J Biol, 2007;6(1):2.
Itoh Y[1], Melamed E[1], Yang X[2], Kampf K[1], Wang S[2], Yehya N[2], Van Nas A[2], Replogle K[3], Band MR[4], Clayton DF[3], Schadt EE[5], Lusis AJ[2], Arnold AP[1]
Affiliations
PMID: 17352797DOI: 10.1186/jbiol53
Abstract
background: In animals with heteromorphic sex chromosomes, dosage compensation of sex-chromosome genes is thought to be critical for species survival. Diverse molecular mechanisms have evolved to effectively balance the expressed dose of X-linked genes between XX and XY animals, and to balance expression of X and autosomal genes. Dosage compensation is not understood in birds, in which females (ZW) and males (ZZ) differ in the number of Z chromosomes.
results: Using microarray analysis, we compared the male:female ratio of expression of sets of Z-linked and autosomal genes in two bird species, zebra finch and chicken, and in two mammalian species, mouse and human. Male:female ratios of expression were significantly higher for Z genes than for autosomal genes in several finch and chicken tissues. In contrast, in mouse and human the male:female ratio of expression of X-linked genes is quite similar to that of autosomal genes, indicating effective dosage compensation even in humans, in which a significant percentage of genes escape X-inactivation.
conclusion: Birds represent an unprecedented case in which genes on one sex chromosome are expressed on average at constitutively higher levels in one sex compared with the other. Sex-chromosome dosage compensation is surprisingly ineffective in birds, suggesting that some genomes can do without effective sex-specific sex-chromosome dosage compensation mechanisms.
MeSH terms
Animals; Chick Embryo; Chickens; Dosage Compensation, Genetic; Female; Finches; Gene Dosage; Gene Expression Profiling; Humans; Male; Mice; Oligonucleotide Array Sequence Analysis; Sex Chromosomes; Sex Ratio
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