Abstract
The Z and W sex chromosomes of birds have evolved independently from the mammalian X and Y chromosomes [1]. Unlike mammals, female birds are heterogametic (ZW), while males are homogametic (ZZ). Therefore male birds, like female mammals, carry a double dose of sex-linked genes relative to the other sex. Other animals with nonhomologous sex chromosomes possess "dosage compensation" systems to equalize the expression of sex-linked genes. Dosage compensation occurs in animals as diverse as mammals, insects, and nematodes, although the mechanisms involved differ profoundly [2]. In birds, however, it is widely accepted that dosage compensation does not occur [3-5], and the differential expression of Z-linked genes has been suggested to underlie the avian sex-determination mechanism [6]. Here we show equivalent expression of at least six of nine Z chromosome genes in male and female chick embryos by using real-time quantitative PCR [7]. Only the Z-linked ScII gene, whose ortholog in Caenorhabditis elegans plays a crucial role in dosage compensation [8], escapes compensation by this assay. Our results imply that the majority of Z-linked genes in the chicken are dosage compensated.
Original language | English |
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Pages (from-to) | 253-7 |
Number of pages | 5 |
Journal | Current biology : CB |
Volume | 11 |
Issue number | 4 |
Publication status | Published - 2001 |
Keywords
- Aconitate Hydratase/genetics
- Actins/genetics
- Animals
- Avian Proteins
- Birds/genetics
- Chick Embryo
- DNA-Binding Proteins/genetics
- Dosage Compensation, Genetic
- Female
- Follistatin
- Glycoproteins/genetics
- Growth Hormone/genetics
- Male
- Nuclear Proteins/genetics
- Sex Chromosomes
- Transcription Factors/genetics