Maintenance of the Three Sex Chromosome Polymorphism in the Platyfish, Xiphophorus maculatus

Evolution ◽  
1980 ◽  
Vol 34 (4) ◽  
pp. 663 ◽  
Author(s):  
Steven Hecht Orzack ◽  
Joel J. Sohn ◽  
Klaus D. Kallman ◽  
Simon A. Levin ◽  
Ross Johnston
Keyword(s):  
Sex Chromosome ◽  
Chromosome Polymorphism ◽  
Xiphophorus Maculatus

scholarly journals MAINTENANCE OF THE THREE SEX CHROMOSOME POLYMORPHISM IN THE PLATYFISH, XIPHOPHORUS MACULATUS

Evolution ◽  
1980 ◽  
Vol 34 (4) ◽  
pp. 663-672 ◽  
Author(s):  
Steven Hecht Orzack ◽  
Joel J. Sohn ◽  
Klaus D. Kallman ◽  
Simon A. Levin ◽  
Ross Johnston
Keyword(s):  
Sex Chromosome ◽  
Chromosome Polymorphism ◽  
Xiphophorus Maculatus

On the Maintenance of Sex Chromosome Polymorphism by Sex-Antagonistic Selection

2011 ◽  
Vol 178 (4) ◽  
pp. 515-524 ◽  
Author(s):  
Olivier Blaser ◽  
Samuel Neuenschwander ◽  
Nicolas Perrin
Keyword(s):  
Sex Chromosome ◽  
Chromosome Polymorphism ◽  
Antagonistic Selection ◽  
Maintenance Of Sex

scholarly journals The evolution of the Y chromosome with X-Y recombination.

Genetics ◽  
1988 ◽  
Vol 119 (3) ◽  
pp. 711-720
Author(s):  
A G Clark
Keyword(s):  
Natural Selection ◽  
Y Chromosome ◽  
Meiotic Recombination ◽  
Population Genetic ◽  
Sex Chromosome ◽  
Genetic Model ◽  
Chromosome Polymorphism ◽  
Significant Finding ◽  
Special Cases ◽  
Theoretical Population

Abstract A theoretical population genetic model is developed to explore the consequences of X-Y recombination in the evolution of sex chromosome polymorphism. The model incorporates one sex-determining locus and one locus subject to natural selection. Both loci have two alleles, and the rate of classical meiotic recombination between the loci is r. The alleles at the sex-determining locus specify whether the chromosome is X or Y, and the alleles at the selected locus are arbitrarily labeled A and a. Natural selection is modeled as a process of differential viabilities. The system can be expressed in terms of three recurrence equations, one for the frequency of A on the X-bearing gametes produced by females, one for each of the frequency of A on the X- and Y-bearing gametes produced by males. Several special cases are examined, including X chromosome dominance and symmetric selection. Unusual equilibria are found with the two sexes having very different allele frequencies at the selected locus. A significant finding is that the allowance of recombination results in a much greater opportunity for polymorphism of the Y chromosome. Tighter linkage results in a greater likelihood for equilibria with a large difference between the sex chromosomes in allele frequency.

Speciation in black flies

Genome ◽  
1989 ◽  
Vol 32 (4) ◽  
pp. 500-509 ◽  
Author(s):  
Klaus Rothfels
Keyword(s):  
Sex Chromosomes ◽  
Sex Chromosome ◽  
Sympatric Speciation ◽  
Chromosome Polymorphism ◽  
Black Flies ◽  
Closely Related Species ◽  
Black Fly ◽  
Progressive Development ◽  
Temporal Relationships ◽  
Species Pairs

In many Simuliidae, patterns of spatial and temporal relationships among the most closely related species are more readily interpreted in terms of sympatric speciation than of allopatric speciation. Specific examples are (i) the allotriploid taxa in Gymnopais and other genera, (ii) the black fly faunas of geologically recent islands (Tahiti), and (iii) species in Prosimulium onychodactylum, a prototype of a continental multisibling species complex. A model of sympatric speciation is presented based on coadaptation of polymorphic sex chromosomes in pairs reinforced by progressive development of assortative mating. This model predicts that (i) populations should frequently exhibit sex-chromosome polymorphism, (ii) these sex-chromosome polymorphisms, and autosomal ones, should in some cases display linkage or association disequilibria, (iii) species pairs or complexes should be incurred that differ only in sex chromosomes and that share extensive ancestral autosomal polymorphisms, and (iv) such species should differ in their biology and perhaps their present-day distribution. Recent publications and observations are in accordance, in general, with predictions from the model. Genetic control, e.g., of diapause, larval developmental timing, and niche preference or ethology, could substitute as a basis of incipient cleavage. The evidence for sympatric speciation is purely inferential, but this is equally true for the allopatric interpretation, and in black flies the circumstantial evidence for prevalence of sympatric speciation appears more compelling. This is not to deny the efficacy of allopatry and founder effect in the origin of some species complexes.Key words: sympatric speciation, black fly, evolution.

Sex Chromosome Polymorphism in Domestic Cattle

1968 ◽  
Vol 59 (1) ◽  
pp. 35-36 ◽  
Author(s):  
NAT M. KIEFFER ◽  
T. C. CARTWRIGHT
Keyword(s):  
Sex Chromosome ◽  
Chromosome Polymorphism

Inter-population sex chromosome polymorphism in the grasshopper Podisma pedestris

Chromosoma ◽  
1970 ◽  
Vol 31 (3) ◽  
pp. 291-308 ◽  
Author(s):  
B. John ◽  
G. M. Hewitt
Keyword(s):  
Sex Chromosome ◽  
Chromosome Polymorphism

scholarly journals Homology of melanoma-inducing loci in the genus Xiphophorus.

Genetics ◽  
1990 ◽  
Vol 126 (4) ◽  
pp. 1083-1091 ◽  
Author(s):  
M Schartl
Keyword(s):  
Receptor Tyrosine Kinase ◽  
Sex Chromosome ◽  
Duplication Event ◽  
Molecular Probes ◽  
Fish Populations ◽  
Gene Duplication Event ◽  
Oncogenic Potential ◽  
Mendelian Genetics ◽  
Xiphophorus Maculatus ◽  
Different Populations

Abstract Several species of the genus Xiphophorus are polymorphic for specific pigment patterns. Some of these give rise to malignant melanoma following the appropriate crossings. For one of these pattern loci from the playfish Xiphophorus maculatus the melanoma-inducing gene has been cloned and found to encode a novel receptor tyrosine kinase, designated Xmrk. Using molecular probes from this gene in Southern blot analyses on single fish DNA preparations from 600 specimens of different populations of various species of the genus Xiphophorus and their hybrids, either with or without melanoma-predisposing pattern, it was shown that all individuals contain the Xmrk gene as a proto-oncogene. It is located on the sex chromosome. All fish that carry a melanoma-predisposing locus which has been identified by Mendelian genetics contain an additional copy of Xmrk, closely linked to a specific melanophore pattern locus on the sex chromosome. The melanoma-inducing loci of the different species and populations are homologous. The additional copy of Xmrk obviously arose by a gene-duplication event, thereby acquiring the oncogenic potential. The homology of the melanoma-inducing loci points to a similar mechanism of tumor suppression in all feral fish populations of the different species of the genus Xiphophorus.

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