Sex biased gene expression in 17 weeks old chicken (ovary, testes)

Sex chromosomes are characterized by a non-random content of genes with preferential expression in one sex. The mechanisms which are responsible for this phenomenon are, however, largely unresolved. To elucidate selective forces shaping the Z chromosome gene content in chicken, we analyzed microarray data from adult and embryonic gonads (the latter already available in GEO Series GSE8693). Total RNA from gonads of 8 males and 8 females was used for hybridization to Affymetrix GeneChip® Chicken Genome Arrays. Prior to hybridization the samples were combined in equal quantities into 4 pools (4 testes/ovary samples in each pool), 2 of them representing testis and 2 ovary. All four GeneChips met Affymetrix quality control criteria. Furthermore, all chips were checked by methods based on probe level robust linear model fitting provided by "affyPLM" package (Bolstad, 2007). None of the chips showed any signs of abnormality.