scholarly journals Chromosomal variation, macroevolution and possible parapatric speciation in Mepraia spinolai (Porter) (Hemiptera: Reduviidae)

1998 ◽  
Vol 21 (2) ◽  
pp. 179-184 ◽  
Author(s):  
Daniel Frias ◽  
Juan Atria
Keyword(s):  
Y Chromosome ◽  
Morphological Changes ◽  
Metropolitan Region ◽  
Southern Population ◽  
Y Chromosomes ◽  
Determination System ◽  
Sex Determination System ◽  
Parapatric Speciation ◽  
Or Genes ◽  
Experimental Crosses

Mepraia spinolai is an endemic species in Chile that lives in wild and domestic habitats. It is the only species of the Reduviidae family that shows alate polymorphism; females are always wingless, but males can be found with and without wings. The M. spinolai karyotype consists of 10 pairs of autosomes and a complex sex determination system. Males from the northernmost regions I and II (latitude 18°-26° South) are always winged (braquipterous) and are X1X2Y, with a large Y chromosome. From region III to the metropolitan region (latitude 26°-33° South), males may be either winged or wingless but appear to be polymorphic for a small neo-Y chromosome, which may have originated by fracture of the large holocentric Y chromosome found in populations from farther north. Experimental crosses suggest that the genes for wings are linked in the Y chromosome and also that there are two cytologically indistinguishable types of neo-Y chromosomes. One form (Y1) bears a gene or genes for wings while the other (Y2) lacks such genes. Males that are X1X2Y1, X1X2Y1Y1 and X1X2Y1Y2 are winged, while the absence of Y1 (X1X2Y2 and X1X2Y2Y2 ) results in a wingless male. These chromosomes and morphological changes are correlated with a shift of the southern population into more arid habitats of the interior in the metropolitan region and region III.

SEX AND SUPERNUMERARY CHROMOSOMES IN THE DIOECIOUS GRASS SOHNSIA FILIFOLIA

1972 ◽  
Vol 14 (1) ◽  
pp. 175-180 ◽  
Author(s):  
D. N. Singh
Keyword(s):  
Sex Determination ◽  
Y Chromosome ◽  
Supernumerary Chromosome ◽  
The Other ◽  
Male Plant ◽  
Diploid Male ◽  
Male And Female ◽  
Supernumerary Chromosomes ◽  
Determination System ◽  
Sex Determination System

A dioecious grass Sohnsia filifolia (Fourn.) Airy Shaw (Syn. Calamochloa filifolia Fourn.) from Mexico has been found to have 2n = 20 chromosomes in both male and female plants. The staminate plants have one chromosome much longer than the other chromosomes of the complement. One pistillate plant was found to have 30 chromosomes, among which the largest chromosome is quite similar to the largest component of the diploid male plant. The longest chromosome has been designated as the Y chromosome. An XY-mechanism of the Drosophilia type has been suggested for the sex determination system in this species. One small supernumerary chromosome was observed in the microsporocytes of some male plants, but was absent in roots.

Invasive Asian Carps in North America

2011 ◽  
Keyword(s):  
Death Rate ◽  
Normal Population ◽  
Fish Population ◽  
Exotic Fish ◽  
Y Chromosomes ◽  
Eradication Strategy ◽  
Determination System ◽  
Normal Fish ◽  
Asian Carps ◽  
Sex Determination System

<em>Abstract</em>.—The directed extinction of an exotic fish population is proposed using a genetic approach to drastically reduce the ratio of females to males within the population. In the proposed strategy, sex-reversed female fish containing two Y chromosomes (Fyy) are introduced into a normal fish population. The frequencies of each of the four expected genotypes of fish in the simulated population (Fxx, Fyy, Mxy, and Myy) were modeled with a set of coupled ordinary differential equations. The equations take into account birth rate, death rate, and a fixed carrying capacity of the system. Using computer-generated simulations, it was determined that the continuous introduction of a relatively small proportion of Fyy females to the normal population leads to extinction of the exotic fish over time. The proposed eradication strategy is relevant to fish species with an XY sex-determination system that tolerate a YY genotype. Published literature suggests that Asian carps are likely to fulfill these criteria. However, technical barriers associated with sex reversal in Asian carps presently exist and must be overcome before implementation of a YY eradication strategy for Asian carps can be considered in practice. An idealized theoretical model for the eradication of Asian carps is thus presented.

WHITE EYE AND CURLED, RECESSIVE MUTANTS ON THE X CHROMOSOME OF ANOPHELES ALBIMANUS

1982 ◽  
Vol 24 (6) ◽  
pp. 661-665 ◽  
Author(s):  
J. A. Seawright ◽  
M. Q. Benedict ◽  
S. Narang ◽  
P. E. Kaiser
Keyword(s):  
Sex Determination ◽  
X Chromosome ◽  
Anopheles Albimanus ◽  
Recessive Lethal ◽  
Y Chromosomes ◽  
Determination System ◽  
Sex Determination System ◽  
Mode Of Inheritance

Two new mutants, white eye (we) and curled (cr), of Anopheles albimanus Wiedemann were isolated and studied. Both mutants are recessive and are approximately 18.9 ± 1.9 units apart on the X chromosome. White eye is fully viable, but cr is a recessive lethal. The mode of inheritance of these two mutants provides further evidence of an X-Y sex determination system in An. albimanus and a lack of homology between the X and Y chromosomes.

scholarly journals The Snakeskin Gourami (Trichopodus pectoralis) Tends to Exhibit XX/XY Sex Determination

Fishes ◽  
2021 ◽  
Vol 6 (4) ◽  
pp. 43
Author(s):  
Thitipong Panthum ◽  
Nararat Laopichienpong ◽  
Ekaphan Kraichak ◽  
Worapong Singchat ◽  
Dung Ho My Nguyen ◽  
...  
Keyword(s):  
Sex Differences ◽  
Sex Determination ◽  
Y Chromosome ◽  
Cytogenetic Analysis ◽  
Genotyping By Sequencing ◽  
Sexually Dimorphic ◽  
Determination System ◽  
Sex Determination System ◽  
Male Specific ◽  
Determination Mechanism

The snakeskin gourami (Trichopodus pectoralis) has a high meat yield and is one of the top five aquaculture freshwater fishes in Thailand. The species is not externally sexually dimorphic, and its sex determination system is unknown. Understanding the sex determination system of this species will contribute to its full-scale commercialization. In this study, a cytogenetic analysis did not reveal any between-sex differences in chromosomal patterns. However, we used genotyping-by-sequencing to identify 4 male-linked loci and 1 female-linked locus, indicating that the snakeskin gourami tends to exhibit an XX/XY sex determination system. However, we did not find any male-specific loci after filtering the loci for a ratio of 100:0 ratio of males:females. This suggests that the putative Y chromosome is young and that the sex determination region is cryptic. This approach provides solid information that can help identify the sex determination mechanism and potential sex determination regions in the snakeskin gourami, allowing further investigation of genetic improvements in the species.

scholarly journals Two Y chromosome-encoded genes determine sex in kiwifruit

2019 ◽  
Author(s):  
Takashi Akagi ◽  
Sarah M. Pilkington ◽  
Erika Varkonyi-Gasic ◽  
Isabelle M. Henry ◽  
Shigeo S. Sugano ◽  
...  
Keyword(s):  
Y Chromosome ◽  
Theoretical Models ◽  
Flowering Plant ◽  
Dioecious Species ◽  
Determination System ◽  
Angiosperm Species ◽  
Sex Determination System ◽  
Male Specific ◽  
Evolution Of Dioecy ◽  
Insight Into

ABSTRACTDioecy, the presence of male and female individuals, has evolved independently in multiple flowering plant lineages. Although theoretical models for the evolution of dioecy, such as the “two-mutation” model, are well established, little is known about the specific genes determining sex and their evolutionary history. Kiwifruit, a major tree crop consumed worldwide, is a dioecious species. In kiwifruit, we had previously identified a Y-encoded sex-determinant candidate gene acting as the suppressor of feminization (SuF), named Shy Girl (SyGI). Here, we identified a second Y-encoded sex-determinant that we named Friendly boy (FrBy), which exhibits strong expression in tapetal cells. Gene-editing and complementation analyses in Arabidopsis thaliana and Nicotiana tabacum indicated that FrBy acts for the maintenance of male (M) functions, independently of SyGI, and that these functions are conserved across angiosperm species. We further characterized the genomic architecture of the small (< 1 Mb) male specific region of the Y-chromosome (MSY), which harbors only two genes significantly expressed in developing gynoecia and androecia, respectively: SyGI and FrBy. Resequencing of the genome of a natural hermaphrodite kiwifruit revealed that this individual is genetically male but carries deletion(s) of parts of the Y-chromosome, including SyGI. Additionally, expression of FrBy in female kiwifruit resulted in hermaphrodite plants. These results clearly indicate that Y-encoded SyGI and FrBy act independently as the SuF and M factors in kiwifruit, respectively, and provide insight into the evolutionary path leading to a two-factor sex determination system but also a new breeding approach for dioecious species.

scholarly journals Heterochiasmy facilitated the establishment of gsdf as a novel sex determining gene in Atlantic halibut

2020 ◽  
Author(s):  
Rolf Brudvik Edvardsen ◽  
Ola Wallerman ◽  
Tomasz Furmanek ◽  
Lene Kleppe ◽  
Patric Jern ◽  
...  
Keyword(s):  
Sex Determination ◽  
Y Chromosome ◽  
Meiotic Recombination ◽  
Sequence Divergence ◽  
Atlantic Halibut ◽  
Specific Expression ◽  
Repeat Class ◽  
Determination System ◽  
Sex Determination System ◽  
Male Specific

Atlantic Halibut (Hippoglossus hippoglossus) has a X/Y genetic sex determination system, but the sex determining factor is not known. We produced a high-quality genome assembly and identified parts of chromosome 13 as the Y chromosome due to sequence divergence between sexes and segregation of sex genotypes in pedigrees. Linkage analysis revealed that all chromosomes exhibit heterochiasmy, i.e. male- and female restricted meiotic recombination intervals (MRR/FRR). We show that FRR/MRR intervals differ in nucleotide diversity and repeat class content and that this is true also for other Pleuronectidae species. We further show that remnants of a Gypsy-like transposable element insertion on chr13 promotes early male specific expression of gonadal somatic cell derived factor (gsdf). Less than 4 MYA, this male-determining element evolved on an autosomal FRR segment featuring pre-existing male meiotic recombination barriers, thereby creating a Y chromosome. We propose that heterochiasmy may facilitate the evolution of genetic sex determination systems.

scholarly journals Telomere-to-telomere assembly of a fish Y chromosome reveals the origin of a young sex chromosome pair

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Lingzhan Xue ◽  
Yu Gao ◽  
Meiying Wu ◽  
Tian Tian ◽  
Haiping Fan ◽  
...  
Keyword(s):  
Y Chromosome ◽  
Sex Chromosomes ◽  
Chromosome Pair ◽  
Sex Chromosome ◽  
Structural Variations ◽  
Recombination Suppression ◽  
Chromosome Differentiation ◽  
Y Chromosomes ◽  
Recent Origin ◽  
Mastacembelus Armatus

Abstract Background The origin of sex chromosomes requires the establishment of recombination suppression between the proto-sex chromosomes. In many fish species, the sex chromosome pair is homomorphic with a recent origin, providing species for studying how and why recombination suppression evolved in the initial stages of sex chromosome differentiation, but this requires accurate sequence assembly of the X and Y (or Z and W) chromosomes, which may be difficult if they are recently diverged. Results Here we produce a haplotype-resolved genome assembly of zig-zag eel (Mastacembelus armatus), an aquaculture fish, at the chromosomal scale. The diploid assembly is nearly gap-free, and in most chromosomes, we resolve the centromeric and subtelomeric heterochromatic sequences. In particular, the Y chromosome, including its highly repetitive short arm, has zero gaps. Using resequencing data, we identify a ~7 Mb fully sex-linked region (SLR), spanning the sex chromosome centromere and almost entirely embedded in the pericentromeric heterochromatin. The SLRs on the X and Y chromosomes are almost identical in sequence and gene content, but both are repetitive and heterochromatic, consistent with zero or low recombination. We further identify an HMG-domain containing gene HMGN6 in the SLR as a candidate sex-determining gene that is expressed at the onset of testis development. Conclusions Our study supports the idea that preexisting regions of low recombination, such as pericentromeric regions, can give rise to SLR in the absence of structural variations between the proto-sex chromosomes.

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