Sex chromosomes in some amniotes share linkage homologies with distantly related taxa in regions orthologous to squamate reptile chromosome 2 (SR2) and the snake W sex chromosome. Thus, the SR2 and W chromosomes may formerly have been part of a larger ancestral amniote super-sex chromosome. Comparison of various sex chromosomal linkage homologies in Toxicofera with those in other amniotes offers an excellent model to assess key cytological differences, to understand the mechanisms of amniote sex chromosome evolution in each lineage and the existence of an ancestral amniote super-sex chromosome. Chromosome maps of four species of Toxicofera were constructed using bacterial artificial chromosomes (BACs) derived from chicken and zebra finch libraries containing amniote sex chromosomal linkages. Different macrochromosome linkage homologies were highly conserved among Toxicofera, and at least two BACs (CH261-125F1 and CH261-40D6) showed partial homology with sex chromosomes of amniotes associated with SR2, which supports the hypothesis of an ancestral super-sex chromosome with overlaps of partial linkage homologies. The present data also suggest a possible multiple fission mechanism of an ancestral super-sex chromosome, which resulted in further development of various sex chromosomal linkages of Toxicofera based on particular properties that favored the role of sex chromosomes.

中文翻译：

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蛇，监控蜥蜴和鬣蜥蜥蜴的性染色体是由“祖先羊膜超性染色体”的多次裂变产生的吗？

在与鳞状爬行动物染色体2（SR2）和蛇W性染色体直系同源的区域中，某些羊膜动物的性染色体与远缘分类群共享连锁同源性。因此，SR2和W染色体以前可能是较大的祖先羊膜超性染色体的一部分。弓形虫与其他羊膜动物的各种性染色体连锁同源性的比较为评估关键细胞学差异，了解每个谱系中羊膜性染色体进化的机制以及祖先羊膜超性别染色体的存在提供了一个极好的模型。使用来源于含有羊膜性染色体连锁的鸡和斑马雀科文库的细菌人工染色体（BAC），构建了四种弓形虫的染色体图。弓形虫之间高度保守的不同染色体同源性很高，并且至少两个BAC（CH261-125F1和CH261-40D6）与与SR2相关的羊膜性染色体具有部分同源性，这支持了祖先超性染色体重叠的假说。部分链接同源性。本数据还提出了祖先超性染色体的可能的多裂变机制，其基于有利于性染色体作用的特定特性，导致了弓形虫的各种性染色体连锁的进一步发展。它支持具有部分连锁同源性重叠的祖先超性染色体的假说。本数据还提出了祖先超性染色体的可能的多裂变机制，其基于有利于性染色体作用的特定特性，导致了弓形虫的各种性染色体连锁的进一步发展。它支持具有部分连锁同源性重叠的祖先超性染色体的假说。本数据还提出了祖先超性染色体的可能的多裂变机制，其基于有利于性染色体作用的特定特性，导致了弓形虫的各种性染色体连锁的进一步发展。