Sex-Chromosome Inversions in Chironomus

1957 ◽  
Vol 91 (856) ◽  
pp. 57-59 ◽  
Author(s):  
A. B. Acton
Keyword(s):  
Sex Chromosome ◽  
Chromosome Inversions

scholarly journals Network Analysis of Linkage Disequilibrium Reveals Genome Architecture in Chum Salmon

2020 ◽  
Vol 10 (5) ◽  
pp. 1553-1561 ◽  
Author(s):  
Garrett McKinney ◽  
Megan V. McPhee ◽  
Carita Pascal ◽  
James E. Seeb ◽  
Lisa W. Seeb
Keyword(s):  
Population Structure ◽  
Linkage Disequilibrium ◽  
Network Analysis ◽  
Chum Salmon ◽  
Sex Chromosome ◽  
Natural Populations ◽  
Population Substructure ◽  
Chromosome Inversion ◽  
Genomic Features ◽  
Chromosome Inversions

Many studies exclude loci that exhibit linkage disequilibrium (LD); however, high LD can signal reduced recombination around genomic features such as chromosome inversions or sex-determining regions. Chromosome inversions and sex-determining regions are often involved in adaptation, allowing for the inheritance of co-adapted gene complexes and for the resolution of sexually antagonistic selection through sex-specific partitioning of genetic variants. Genomic features such as these can escape detection when loci with LD are removed; in addition, failing to account for these features can introduce bias to analyses. We examined patterns of LD using network analysis to identify an overlapping chromosome inversion and sex-determining region in chum salmon. The signal of the inversion was strong enough to show up as false population substructure when the entire dataset was analyzed, while the effect of the sex-determining region on population structure was only obvious after restricting analysis to the sex chromosome. Understanding the extent and geographic distribution of inversions is now a critically important part of genetic analyses of natural populations. Our results highlight the importance of analyzing and understanding patterns of LD in genomic dataset and the perils of excluding or ignoring loci exhibiting LD. Blindly excluding loci in LD would have prevented detection of the sex-determining region and chromosome inversion while failing to understand the genomic features leading to high-LD could have resulted in false interpretations of population structure.

scholarly journals Extensive Recombination Suppression and Epistatic Selection Causes Chromosome-Wide Differentiation of a Selfish Sex Chromosome in Drosophila pseudoobscura

Genetics ◽  
2020 ◽  
Vol 216 (1) ◽  
pp. 205-226 ◽  
Author(s):  
Zachary L. Fuller ◽  
Spencer A. Koury ◽  
Christopher J. Leonard ◽  
Randee E. Young ◽  
Kobe Ikegami ◽  
...  
Keyword(s):  
Population Genetic ◽  
Sex Chromosome ◽  
Chromosomal Rearrangements ◽  
Comparative Genomic ◽  
Recombination Suppression ◽  
Mendelian Segregation ◽  
Multiple Alleles ◽  
Chromosome Inversions ◽  
Combined Action ◽  
The Right

Sex-Ratio (SR) chromosomes are selfish X-chromosomes that distort Mendelian segregation and are commonly associated with inversions. These chromosomal rearrangements suppress recombination with Standard (ST) X-chromosomes and are hypothesized to maintain multiple alleles important for distortion in a single large haplotype. Here, we conduct a multifaceted study of the multiply inverted Drosophila pseudoobscura SR chromosome to understand the evolutionary history, genetic architecture, and present-day dynamics that shape this enigmatic selfish chromosome. The D. pseudoobscura SR chromosome has three nonoverlapping inversions of the right arm of the metacentric X-chromosome: basal, medial, and terminal. We find that 23 of 29 Mb of the D. pseudoobscuraX-chromosome right arm is highly differentiated between the Standard and SR arrangements, including a 6.6 Mb collinear region between the medial and terminal inversions. Although crossing-over is heavily suppressed on this chromosome arm, we discover it is not completely eliminated, with measured rates indicating recombination suppression alone cannot explain patterns of differentiation or the near-perfect association of the three SR chromosome inversions in nature. We then demonstrate the ancient basal and medial inversions of the SR chromosome contain genes sufficient to cause weak distortion. In contrast, the younger terminal inversion cannot distort by itself, but contains at least one modifier gene necessary for full manifestation of strong sex chromosome distortion. By parameterizing population genetic models for chromosome-wide linkage disequilibrium with our experimental results, we infer that strong selection acts to maintain the near-perfect association of SR chromosome inversions in present-day populations. Based on comparative genomic analyses, direct recombination experiments, segregation distortion assays, and population genetic modeling, we conclude the combined action of suppressed recombination and strong, ongoing, epistatic selection shape the D. pseudoobscura SR arrangement into a highly differentiated chromosome.

scholarly journals Patterns of linkage disequilibrium reveal genome architecture in chum salmon

2019 ◽  
Author(s):  
Garrett McKinney ◽  
Megan V. McPhee ◽  
Carita Pascal ◽  
James E. Seeb ◽  
Lisa W. Seeb
Keyword(s):  
Linkage Disequilibrium ◽  
Chum Salmon ◽  
Sex Chromosome ◽  
Natural Populations ◽  
Population Substructure ◽  
Chromosome Inversion ◽  
Genomic Features ◽  
Chromosome Inversions ◽  
Sexually Antagonistic Selection ◽  
Gene Complexes

AbstractMany studies exclude loci exhibiting linkage disequilibrium (LD); however, high LD can signal reduced recombination around genomic features such as chromosome inversions or sex-determining regions. Chromosome inversions and sex-determining regions are often involved in adaptation, allowing for the inheritance of co-adapted gene complexes and for the resolution of sexually antagonistic selection through sex-specific partitioning of genetic variants. Genomic features such as these can escape detection when loci with LD are removed; in addition, failing to account for these features can introduce bias to analyses. We examined patterns of LD using network analysis to identify an overlapping chromosome inversion and sex-determining region in chum salmon. The signal of the inversion was strong enough to show up as false population substructure when the entire dataset was analyzed, while the signal of the sex-determining region was only obvious after restricting genetic analysis to the sex chromosome. Understanding the extent and geographic distribution of inversions is now a critically important part of genetic analyses of natural populations. The results of this study highlight the importance of analyzing and understanding patterns of LD in genomic dataset and the perils of ignoring or excluding loci exhibiting LD.

Latitudinal differences in sex chromosome inversions, sex linked allozymes, and mitochondrial DNA variation in Drosophila subobscura

Genetica ◽  
1993 ◽  
Vol 92 (1) ◽  
pp. 67-74 ◽  
Author(s):  
J. M. Larruga ◽  
J. Rozas ◽  
M. Hern�ndez ◽  
A. M. Gonz�lez ◽  
V. M. Cabrera
Keyword(s):  
Mitochondrial Dna ◽  
Sex Chromosome ◽  
Drosophila Subobscura ◽  
Dna Variation ◽  
Chromosome Inversions

Sex chromosome inversions enforce reproductive isolation across an avian hybrid zone

2018 ◽  
Vol 28 (6) ◽  
pp. 1246-1262 ◽  
Author(s):  
Daniel M. Hooper ◽  
Simon C. Griffith ◽  
Trevor D. Price
Keyword(s):  
Reproductive Isolation ◽  
Hybrid Zone ◽  
Sex Chromosome ◽  
Chromosome Inversions

scholarly journals Range Overlap Drives Chromosome Inversion Fixation in Passerine Birds

2016 ◽  
Author(s):  
Daniel M. Hooper
Keyword(s):  
Pericentric Inversion ◽  
Sex Chromosome ◽  
Gc Content ◽  
Divergence Times ◽  
Passerine Birds ◽  
Genomic Context ◽  
Chromosome Inversion ◽  
Closely Related Species ◽  
Chromosome Inversions ◽  
Range Overlap

Chromosome inversions evolve frequently but the reasons why remain largely enigmatic. I used cytological descriptions of 410 species of passerine birds (order Passeriformes) to identify pericentric inversion differences between species. Using a new fossil-calibrated phylogeny I examine the phylogenetic, demographic, and genomic context in which these inversions have evolved. The number of inversion differences between closely related species was highly variable yet consistently predicted by a single factor: whether the ranges of species overlapped. This observation holds even when the analysis is restricted to sympatric sister pairs known to hybridize, and which have divergence times estimated similar to allopatric pairs. Inversions were significantly more likely to have fixed on a sex chromosome than an autosome yet variable mutagenic input alone (by chromosome size, map length, GC content, or repeat density) cannot explain the differences between chromosomes in the number of inversions fixed. Together, these results support a model in which inversions in passerines are adaptive and spread by selection when gene flow occurs before reproductive isolation is complete.

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