{"OA_embargo":"6","corr_author":"1","department":[{"_id":"GradSch"},{"_id":"BeVi"}],"OA_place":"repository","year":"2024","acknowledged_ssus":[{"_id":"ScienComp"},{"_id":"CampIT"}],"file":[{"date_created":"2024-11-13T12:15:28Z","title":"Early stages of sex chromosome evolution","file_name":"AMrnjavac_thesis_library.docx","relation":"source_file","file_size":26870629,"creator":"amrnjava","access_level":"closed","embargo_to":"open_access","file_id":"18551","content_type":"application/vnd.openxmlformats-officedocument.wordprocessingml.document","date_updated":"2025-05-11T22:30:04Z","checksum":"3e48b163c22114ef5d5371f758668289"},{"creator":"amrnjava","file_size":4228766,"relation":"main_file","access_level":"open_access","title":"Early stages of sex chromosome evolution","date_created":"2024-11-13T12:15:54Z","file_name":"AMrnjavac_thesis_library.pdf","checksum":"3ead60c1b678e7dcf018043aef3b5db2","date_updated":"2025-05-11T22:30:04Z","embargo":"2025-05-11","file_id":"18552","content_type":"application/pdf"}],"oa":1,"author":[{"full_name":"Mrnjavac, Andrea","id":"353FAC84-AE61-11E9-8BFC-00D3E5697425","last_name":"Mrnjavac","first_name":"Andrea"}],"date_updated":"2025-07-10T11:51:24Z","doi":"10.15479/at:ista:18531","language":[{"iso":"eng"}],"publisher":"Institute of Science and Technology Austria","day":"11","has_accepted_license":"1","_id":"18531","ddc":["576"],"alternative_title":["ISTA Thesis"],"license":"https://creativecommons.org/licenses/by-nc-nd/4.0/","title":"Early stages of sex chromosome evolution","month":"11","user_id":"8b945eb4-e2f2-11eb-945a-df72226e66a9","file_date_updated":"2025-05-11T22:30:04Z","keyword":["Sex chromosomes","evolution","selection","sheltering"],"status":"public","publication_status":"published","tmp":{"short":"CC BY-NC-ND (4.0)","legal_code_url":"https://creativecommons.org/licenses/by-nc-nd/4.0/legalcode","name":"Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)","image":"/images/cc_by_nc_nd.png"},"type":"dissertation","degree_awarded":"PhD","supervisor":[{"full_name":"Vicoso, Beatriz","id":"49E1C5C6-F248-11E8-B48F-1D18A9856A87","first_name":"Beatriz","last_name":"Vicoso","orcid":"0000-0002-4579-8306"}],"date_created":"2024-11-11T08:40:45Z","related_material":{"record":[{"status":"public","relation":"part_of_dissertation","id":"12521"},{"status":"public","relation":"part_of_dissertation","id":"18549"}]},"page":"181","publication_identifier":{"issn":["2663-337X"]},"oa_version":"Published Version","date_published":"2024-11-11T00:00:00Z","abstract":[{"lang":"eng","text":"Sex chromosomes and autosomes exhibit very different evolutionary dynamics.\r\nThe Y chromosome usually degenerates, leaving many X-linked loci hemizygous in\r\nmales. Since recessive X-linked mutations are always exposed to selection in males,\r\nselection is more efficient on the X chromosome than on autosomes on recessive\r\nmutations, leading to faster adaptation on the X chromosome than other genomic\r\nregions, if beneficial mutations are on average recessive (known as the Faster-X\r\neffect). In the presence of the functional, but non-recombining gametolog on the Y (as\r\nis often the case in young non-recombining regions), recessive mutations are\r\nsheltered from selection on the X chromosome. We model this scenario and show that\r\nthe efficiency of selection is reduced on diploid X loci due to sheltering by the Y\r\nchromosome. Reduced efficiency of selection leads to slower adaptation and\r\nincreased accumulation of deleterious mutations (Slower-X effect). We extended this\r\nmodel to explore the effect of sex-specific selection on degeneration of sex\r\nchromosomes, showing theoretically that male-limited genes degenerate on the X\r\nchromosome and female-biased genes degenerate on the Y chromosome. This\r\nprediction depends on the effective population size and the mutation rate, explaining\r\nthe variety of sex chromosome degeneration patterns observed in nature.\r\nTo test for direct evidence of a Slower-X (or Slower-Z) effect, we analyzed the\r\nZW sex chromosomes of the flatworm Schistosoma japonicum, which have a very\r\nyoung non-recombining region with non-degenerated W. Diploid Z-linked genes have\r\nhigher ratios of non-synonymous to synonymous polymorphisms than autosomal\r\ngenes, supporting reduced efficiency of selection on the diploid Z region. These results\r\nprovide evidence of sheltering by the W chromosome, a mechanism that could\r\ncontribute to Z (X) chromosome degeneration, and illustrate contrasting evolutionary\r\npatterns in old and young sex chromosome regions. In addition, genes with sexspecific patterns of expression show opposite patterns of selection in the young\r\n(diploid) and old (hemizygous) Z, showing the complex manner in which sex-specific selection shapes the evolutionary patterns of sex chromosomes. "}],"article_processing_charge":"No","citation":{"ama":"Mrnjavac A. Early stages of sex chromosome evolution. 2024. doi:<a href=\"https://doi.org/10.15479/at:ista:18531\">10.15479/at:ista:18531</a>","chicago":"Mrnjavac, Andrea. “Early Stages of Sex Chromosome Evolution.” Institute of Science and Technology Austria, 2024. <a href=\"https://doi.org/10.15479/at:ista:18531\">https://doi.org/10.15479/at:ista:18531</a>.","apa":"Mrnjavac, A. (2024). <i>Early stages of sex chromosome evolution</i>. Institute of Science and Technology Austria. <a href=\"https://doi.org/10.15479/at:ista:18531\">https://doi.org/10.15479/at:ista:18531</a>","short":"A. Mrnjavac, Early Stages of Sex Chromosome Evolution, Institute of Science and Technology Austria, 2024.","ista":"Mrnjavac A. 2024. Early stages of sex chromosome evolution. Institute of Science and Technology Austria.","ieee":"A. Mrnjavac, “Early stages of sex chromosome evolution,” Institute of Science and Technology Austria, 2024.","mla":"Mrnjavac, Andrea. <i>Early Stages of Sex Chromosome Evolution</i>. Institute of Science and Technology Austria, 2024, doi:<a href=\"https://doi.org/10.15479/at:ista:18531\">10.15479/at:ista:18531</a>."}}