Early stages of sex chromosome evolution (Record no. 768060)
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| 000 -LEADER | |
|---|---|
| fixed length control field | 03206ntm a22002897a 4500 |
| 003 - CONTROL NUMBER IDENTIFIER | |
| control field | AT-ISTA |
| 005 - DATE AND TIME OF LATEST TRANSACTION | |
| control field | 20250915114917.0 |
| 008 - FIXED-LENGTH DATA ELEMENTS--GENERAL INFORMATION | |
| fixed length control field | 250915s2024 au ||||| m||| 00| 0 eng d |
| 040 ## - CATALOGING SOURCE | |
| Transcribing agency | ISTA |
| 100 ## - MAIN ENTRY--PERSONAL NAME | |
| Personal name | Mrnjavac, Andrea |
| 9 (RLIN) | 1084224 |
| 245 ## - TITLE STATEMENT | |
| Title | Early stages of sex chromosome evolution |
| 260 ## - PUBLICATION, DISTRIBUTION, ETC. (IMPRINT) | |
| Name of publisher, distributor, etc. | Institute of Science and Technology Austria |
| Date of publication, distribution, etc. | 2024 |
| 500 ## - GENERAL NOTE | |
| General note | Thesis |
| 505 ## - FORMATTED CONTENTS NOTE | |
| Formatted contents note | Abstract |
| 505 ## - FORMATTED CONTENTS NOTE | |
| Formatted contents note | Acknowledgements |
| 505 ## - FORMATTED CONTENTS NOTE | |
| Formatted contents note | About the Author |
| 505 ## - FORMATTED CONTENTS NOTE | |
| Formatted contents note | List of Collaborators and Publications |
| 505 ## - FORMATTED CONTENTS NOTE | |
| Formatted contents note | Table of Contents |
| 505 ## - FORMATTED CONTENTS NOTE | |
| Formatted contents note | 1 Introduction |
| 505 ## - FORMATTED CONTENTS NOTE | |
| Formatted contents note | 2 Slower-X: Reduced efficiency of selection in the early stages of X chromosome evolution |
| 505 ## - FORMATTED CONTENTS NOTE | |
| Formatted contents note | 3 Effects of sheltering on sex chromosome degeneration and sex-biased gene content evolution |
| 505 ## - FORMATTED CONTENTS NOTE | |
| Formatted contents note | 4 Evidence of a slower-Z effect in Schistosoma japonicum |
| 505 ## - FORMATTED CONTENTS NOTE | |
| Formatted contents note | 5 Discussion |
| 520 ## - SUMMARY, ETC. | |
| Summary, etc. | Sex chromosomes and autosomes exhibit very different evolutionary dynamics. The Y chromosome usually degenerates, leaving many X-linked loci hemizygous in males. Since recessive X-linked mutations are always exposed to selection in males, selection is more efficient on the X chromosome than on autosomes on recessive mutations, leading to faster adaptation on the X chromosome than other genomic regions, if beneficial mutations are on average recessive (known as the Faster-X effect). In the presence of the functional, but non-recombining gametolog on the Y (as is often the case in young non-recombining regions), recessive mutations are sheltered from selection on the X chromosome. We model this scenario and show that the efficiency of selection is reduced on diploid X loci due to sheltering by the Y chromosome. Reduced efficiency of selection leads to slower adaptation and increased accumulation of deleterious mutations (Slower-X effect). We extended this model to explore the effect of sex-specific selection on degeneration of sex chromosomes, showing theoretically that male-limited genes degenerate on the X chromosome and female-biased genes degenerate on the Y chromosome. This prediction depends on the effective population size and the mutation rate, explaining the variety of sex chromosome degeneration patterns observed in nature. To test for direct evidence of a Slower-X (or Slower-Z) effect, we analyzed the ZW sex chromosomes of the flatworm Schistosoma japonicum, which have a very young non-recombining region with non-degenerated W. Diploid Z-linked genes have higher ratios of non-synonymous to synonymous polymorphisms than autosomal genes, supporting reduced efficiency of selection on the diploid Z region. These results provide evidence of sheltering by the W chromosome, a mechanism that could contribute to Z (X) chromosome degeneration, and illustrate contrasting evolutionary patterns in old and young sex chromosome regions. In addition, genes with sexspecific patterns of expression show opposite patterns of selection in the young (diploid) and old (hemizygous) Z, showing the complex manner in which sex-specific selection shapes the evolutionary patterns of sex chromosomes. |
| 856 ## - ELECTRONIC LOCATION AND ACCESS | |
| Uniform Resource Identifier | <a href="https://doi.org/10.15479/at:ista:18531">https://doi.org/10.15479/at:ista:18531</a> |
| 942 ## - ADDED ENTRY ELEMENTS (KOHA) | |
| Source of classification or shelving scheme | Dewey Decimal Classification |
| Withdrawn status | Lost status | Source of classification or shelving scheme | Damaged status | Not for loan | Home library | Current library | Date acquired | Total Checkouts | Full call number | Barcode | Date last seen | Price effective from | Koha item type |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Not Lost | Dewey Decimal Classification | Library | Library | 15/09/2025 | Quiet Room | AT-ISTA#003311 | 16/09/2025 | 15/09/2025 | Book |