Figure 1.
Diversity of frog sex chromosome systems. (a) Homomorphic sex chromosomes—sex-specific haplotype can vary largely from very small to the full length of the homologous X/Z, within or across populations within species. (b) Simple heteromorphic sex chromosomes—the Y/W may be bigger or smaller than X/Z. (c) Y-autosome fusion generating Neo-X (X2) and Neo-Y. (d) Multiple sex chromosomes in Leptodactylus pentadactylus, where 6 pairs of sex chromosomes form a ring shape during meiosis. (e) WO/OO and supernumerary (B) chromosomes in Leiopelma hochstetteri, with population-specific W and various forms of B chromosomes, which are never observed in males. (f) Pie chart shows the proportion of sex chromosome systems in Anuran frogs. All the non-homomorphic sex chromosome types, such as b, c, d and e systems, are heteromorphic.