Somatic sex-specific transcriptome differences in Drosophila revealed by whole transcriptome sequencing. In humans, there is a total of 46 chromosomes or in pair of Intraspecific expression variation We obtained estimates of broad sense heritability for D. Statistical analysis We permuted the chromosomal locations of the genes in our data sets times to estimate a null distribution of the number of genes in each expression class on each chromosome arm in Drosophila and each chromosome in mouse.
In humans, there are 46 or 23 pairs of chromosomes, out of which 22 pairs are autosomes, and a pair is the sex chromosomes or allosomes. A survey of ovary- testis- and soma-biased gene expression in Drosophila melanogaster adults.
Wiley, New York. Furthermore, when we exclude genes on the X chromosome, we observe an increase in bootstrap support for the correct branching order between D. Branch lengths were estimated using the method of Fitch and Margoliash  with a fixed tree topology implemented in the PHYLIP software package .
Table 1. Faster-X expression evolution is not driven by relaxed constraints Accelerated evolutionary divergence can be the result of relaxed selective constraints or an elevated rate of adaptive evolution.
Second, testis-expressed genes tend to be narrowly expressed Meiseland narrowly expressed genes are under-represented on the X chromosome Fig. Therefore, the selection pressures on genes with prostate- and testis-biased expression likely act in a male-limited manner. Genetic Sex Determination Occurs in Different Ways with a Myriad of Outcomes Many different genetic mechanisms of sex determination have been discovered in nature and studied deeply, using molecular-genetic tools reviewed in Cline and Meyer ; Marin and Baker ; Zarkower ; Williams and Carroll ; Charlesworth and Mank ; Gamble and Zarkower ; Hughes and Rozen similarities between sex chromosomes and autosomes define in Tallahassee We chose this approach because, as we introduce more parameters into our analysis, gene-wise expression divergence is easier to interpret than correlations of chromosome-wide expression between species.
Furthermore, new genes with testis- or male-biased expression tend to be preferentially located on the X or Z chromosome in Drosophila Zhang et al. Blackmon and Demuth find that in Adephaga, new Y chromosomes are evolving at the same rate as they are lost, whereas in Polyphaga Y chromosomes are twice as readily gained as lost.
Our expression data from larvae support this hypothesis.
B The locus is X-linked and not dosage compensated with measurements collected in males. For example, the Drosophila accessory gland and the mammalian prostate are both male-limited reproductive organs that contribute seminal proteins to the ejaculate.
Analyses of non-reproductive tissues have also revealed similarities in the X-linkage of genes with sex-biased expression in Drosophila and mammals.