caa a22 4500 445844884 CHVBK 20180317145355.0 cr unu---uuuuu 170323e20110601xx s 000 0 eng 10.1007/s10709-011-9581-1 doi (NATIONALLICENCE)springer-10.1007/s10709-011-9581-1 Pigozzi María Facultad de Medicina, Instituto de Investigaciones en Reproducción, Paraguay 2155 piso 10, C1121ABG, Buenos Aires, Argentina aut Diverse stages of sex-chromosome differentiation in tinamid birds: evidence from crossover analysis in Eudromia elegans and Crypturellus tataupa [Elektronische Daten] [María Pigozzi] All extant birds share the same sex-chromosome system: ZZ males and ZW females with striking differences in the stages of sex-chromosome differentiation between the primitive palaeognathus ratites and the large majority of avian species grouped within neognaths. Evolutionarily close to ratites is the neotropical order Tinamiformes that has been scarcely explored regarding their ZW pair morphology and constitution. Tinamous, when compared to ratites, constitute a large group among Palaeognathae, therefore, exploring the extent of homology between the Z and W chromosomes in this group might reveal key features on the evolution of the avian sex chromosomes. We mapped MLH1 foci that are crossover markers on pachytene bivalents to determine the size and localization of the homologous region shared by the Z and W chromosomes in two tinamous: Eudromia elegans and Crypturellus tataupa. We found that the homologous (pseudoautosomal) region differ significantly in size between these two species. They both have a single recombination event on the long arm of the acrocentric Z and W chromosomes. However, in E. elegans the pseudoautosomal region occupies one-fourth of the W chromosome, while in C. tataupa it is restricted to the tip of the long arm of the W. The W chromosomes in these two species differ in their heterochromatin content: in E. elegans it shows a terminal euchromatic segment and in C. tataupa is completely heterochromatic. These results show that tinamous have ZW pairs with more diversified stages of differentiation compared to ratites. Finally, the idea that the avian proto-sex chromosomes started to diverge from the end of the long arm towards the centromere of an acrocentric pair is discussed. Springer Science+Business Media B.V., 2011 Sex chromosomes nationallicence Tinamiformes nationallicence Birds nationallicence Genetica Springer Netherlands 139/6(2011-06-01), 771-777 0016-6707 139:6<771 2011 139 10709 https://doi.org/10.1007/s10709-011-9581-1 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s10709-011-9581-1 text/html Onlinezugriff via DOI NATIONALLICENCE 100 1- Pigozzi María Facultad de Medicina, Instituto de Investigaciones en Reproducción, Paraguay 2155 piso 10, C1121ABG, Buenos Aires, Argentina aut NATIONALLICENCE 773 0- Genetica Springer Netherlands 139/6(2011-06-01), 771-777 0016-6707 139:6<771 2011 139 10709 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer