Strategies for meiotic sex chromosome dynamics and telomeric elongation in Marsupials
Fig 1
Phylogeny of the marsupial species included in the study.
(A) Phylogenetic relationships of the three marsupial species included in the study, with representation of sex chromosome structure for each species. Human sex chromosomes are included for comparison. Variation in diploid numbers is indicated for each phylogenetic branch. All marsupials lack a pseudo-autosomal region (PAR). The tammar (M. eugenii) X chromosome is large compared to the fat-tailed dunnart (S. crassicaudata) and the fat-tailed mouse opossum (T. elegans). Moreover, the tammar X chromosome bears NOR sequences in the centromeric region and the p-arm contains a region of shared DNA repeats with the q-arm of the Y chromosome [31]. (B) Meiotic karyotypes of the species included in the study: M. eugenii, S. crassicaudata and T. elegans. Karyotypes correspond to primary spermatocytes at pachytene labelled with antibodies against SYCP3 (green) and centromeres (red). The tammar sex chromosomes form a highly condensed dense plate at pachytene.