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Updated: Jun 21, 2025

Dissection of Larval Zebrafish Gonadal Tissue
Published on: April 26, 2017
Comparative genomics illuminates karyotype and sex chromosome evolution of sharks
Jiahong Wu1, Fujiang Liu2, Jie Jiao1
1Integrative Science Center of Germplasm Creation in Western China (Chongqing) Science City, MOE Key Laboratory of Freshwater Fish Reproduction and Development, School of Life Sciences, Southwest University, Chongqing 400715, China.
Abstract:
Chondrichthyes is an important lineage to reconstruct the evolutionary history of vertebrates. Here, we analyzed genome synteny for six chondrichthyan chromosome-level genomes. Our comparative analysis reveals a slow evolutionary rate of chromosomal changes, with infrequent but independent fusions observed in sharks, skates, and chimaeras. The chondrichthyan common ancestor had a proto-vertebrate-like karyotype, including the presence of 18 microchromosome pairs. The X chromosome is a conversed microchromosome shared by all sharks, suggesting a likely common origin of the sex chromosome at least 181 million years ago. We characterized the Y chromosomes of two sharks that are highly differentiated from the X except for a small young evolutionary stratum and a small pseudoautosomal region. We found that shark sex chromosomes lack global dosage compensation but that dosage-sensitive genes are locally compensated. Our study on shark chromosome evolution enhances our understanding of shark sex chromosomes and vertebrate chromosome evolution.
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