The sex-specific region of sex chromosomes in animals and plants

Abstract

Our understanding of the evolution of sex chromosomes has increased greatly in recent years due to a number of molecular evolutionary investigations in divergent sex chromosome systems, and these findings are reshaping theories of sex chromosome evolution. In particular, the dynamics of the sex-determining region (SDR) have been demonstrated by recent findings in ancient and incipient sex chromosomes. Radical changes in genomic structure and gene content in the male specific region of the Y chromosome between human and chimpanzee indicated rapid evolution in the past 6 million years, defying the notion that the pace of evolution in the SDR was fast at early stages but slowed down overtime. The chicken Z and the human X chromosomes appeared to have acquired testisexpressed genes and expanded in intergenic regions. Transposable elements greatly contributed to SDR expansion and aided the trafficking of genes in the SDR and its X or Z counterpart through retrotransposition. Dosage compensation is not a destined consequence of sex chromosomes as once thought. Most X-linked microRNA genes escape silencing and are expressed in testis. Collectively, these findings are challenging many of our preconceived ideas of the evolutionary trajectory and fates of sex chromosomes.

Zebrafish sex: a complicated affair

“…In the best known form of SD that is found in mammals and avians as well as many other vertebrate species, including some teleosts, there is a so-called ‘master switch’ that typically resides on a special chromosomal pair, the well-differentiated sex chromosomes [9, 49, 50]. If the ‘master switch’ is on the ‘heterogametic’ member of the sex chromosomal pair that is present in only one of the two sexes (male-specific Y or female-specific W), then it will initiate the biological programs in representatives of that sex only.…”

Are some chromosomes particularly good at sex? Insights from amniotes

“…Sex determination, the process by which development is directed down the male or female pathway, has been the subject of philosophical interest for millennia (Mittwoch 2000) and rigorous enquiry in more recent times (Bellott and Page 2010;Mank 2011;Ming et al 2011;Ito et al 2011). Even when the focus is narrowed to amniotes (comprising reptiles, birds, and mammals), an astonishing variety of mechanisms determine sex, suggesting frequent evolution and turnover of sex chromosomes as well as sex-determining modes.…”

Circulating microRNAs as novel and sensitive biomarkers of acute myocardial Infarction

“…Indeed, up to 1424 miRNAs are in the miRBase Database (release 17.0, April, 2011) [14,15]. Most of the microRNA genes are located in the introns of protein-coding genes or as independent entities in between the genes [16–19]. As shown in Fig.…”