A new look at the evolution of avian sex chromosomes

@article{Stiglec2007ANL,
  title={A new look at the evolution of avian sex chromosomes},
  author={Rami Stiglec and Tariq Ezaz and Jennifer A. Marshall Graves},
  journal={Cytogenetic and Genome Research},
  year={2007},
  volume={117},
  pages={103 - 109}
}
Birds have a ubiquitous, female heterogametic, ZW sex chromosome system. The current model suggests that the Z chromosome and its degraded partner, the W chromosome, evolved from an ancestral pair of autosomes independently from the mammalian XY male heteromorphic sex chromosomes – which are similar in size, but not gene content (Graves, 1995; Fridolfsson et al., 1998). Furthermore the degradation of the W has been proposed to be progressive, with the basal clade of birds (the ratites… 
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Evolutionary Dynamics of Sex Chromosomes of Paleognathous Birds
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The analysis of Z chromosome evolution and gene expression across 12 paleognaths shows that paleognath Z chromosomes are atypical at the genomic level, but the evolutionary forces maintaining largely homomorphic sex chromosomes in these species remain elusive.
Evolutionary dynamics of sex chromosomes of palaeognathous birds
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It is confirmed at the genomic levels that most palaeognaths (excepting some species of tinamous) retain large PARs, and limited evidence for increased evolutionary rates either across the chromosome or in DRs is found, but signals of faster-Z evolution are recovered similar to neognaths in tinamou species with mostly degenerated W chromosomes.
Triploid plover female provides support for a role of the W chromosome in avian sex determination
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The results suggest a prominent role for a female determining gene on the W chromosome, which implies that avian sex determination is more dynamic and complex than currently envisioned.
INDEPENDENT STRATUM FORMATION ON THE AVIAN SEX CHROMOSOMES REVEALS INTER-CHROMOSOMAL GENE CONVERSION AND PREDOMINANCE OF PURIFYING SELECTION ON THE W CHROMOSOME
TLDR
Evidence from 16 gametologs reveal that the W chromosome is evolving with a significant contribution of purifying selection, consistent with previous findings that W‐linked genes play an important role in encoding sex‐specific fitness.
The long and the short of avian W chromosomes: no evidence for gradual W shortening
TLDR
No support is found for the view that W chromosomes gradually become smaller over evolutionary time, and the length of the W chromosome can fluctuate over short time scales, probably involving both shortening and elongation of non-coding regions.
The Evolution of Sex Chromosome Dosage Compensation in Animals
TLDR
Analysis showed that the fraction of dosage-sensitive housekeeping genes on the sex chromosome is significantly correlated with the S:A ratio, suggesting that the dosage sensitivity states of sex chromosomes is a major factor underlying different evolutionary strategies of dosage compensation.
The ZW sex microchromosomes of an Australian dragon lizard share no homology with those of other reptiles or birds
TLDR
What homology, if any, the sex chromosomes of the Australian dragon lizard Pogona vitticeps shares with those of snake and chicken are determined by mapping the dragon homologs of five snake Z chromosomes genes and five chicken Z chromosome genes to chromosomes in the dragon.
Small but mighty: the evolutionary dynamics of W and Y sex chromosomes
  • J. Mank
  • Biology
    Chromosome Research
  • 2011
Although sex chromosomes have been the focus of a great deal of scientific scrutiny, most interest has centred on understanding the evolution and relative importance of X and Z chromosomes. By…
Genetic evidence against a role for W-linked histidine triad nucleotide binding protein (HINTW) in avian sex determination.
TLDR
Genetic evidence is provided against a dominant role for HINTW in avian sex determination by mis-expressing it in genetically male (ZZ) embryos, using the RCASBP avian retroviral vector.
Rowley Review
TLDR
This review summarises the current understanding of sex determination in birds, with emphasis on the molecular genetics of male versus female development during embryonic life, and the demonstration that the key, sex-linked gene, DMRT1, is required for testis formation and hence male development.
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