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.

Primary sex determination in the nematode C. elegans

Development ◽  
1987 ◽  
Vol 101 (Supplement) ◽  
pp. 5-16 ◽  
Author(s):  
Jonathan Hodgkin
Keyword(s):  
Sex Determination ◽  
X Chromosome ◽  
Germ Line ◽  
X Chromosomes ◽  
C Elegans ◽  
Female Sex ◽  
Determination System ◽  
One Step ◽  
Sex Determination System ◽  
Specific Control

Most nematodes have XO male/XX female sex determination. C. elegans is anomalous, having XX hermaphrodites rather than females. The hermaphrodite condition appears to result from the modification of a basic male/female sex-determination system, which permits both spermatogenesis and oogenesis to occur within a female soma. This modification is achieved by a germ-line-specific control acting at one step in a cascade of autosomal regulatory genes, which respond to X-chromosome dosage and direct male, female, or hermaphrodite development. Mutations of one of these genes can be used to construct artificial strains with ZZ male/WZ female sex determination. Primary sex determination normally depends on the ratio of X chromosomes to autosomes, as in Drosophila, and there appear to be multiple sites on the X chromosome that contribute to this ratio. Also, as in Drosophila, X-chromosome expression is compensated to equalize gene activity in XX and XO animals. Interactions between dosage compensation and sex determination are described and discussed.

scholarly journals Effective Population Sizes for Cytoplasmic and Nuclear Genes in a Gynodioecious Species: The Role of the Sex Determination System

Genetics ◽  
2000 ◽  
Vol 154 (1) ◽  
pp. 447-458
Author(s):  
Valérie Laporte ◽  
Joël Cuguen ◽  
Denis Couvet
Keyword(s):  
Sex Determination ◽  
High Frequency ◽  
Selfing Rate ◽  
Effective Population ◽  
Population Sizes ◽  
Determination System ◽  
Census Number ◽  
Sex Determination System ◽  
Mode Of Inheritance

Abstract Equations are derived for the effective sizes of gynodioecious populations with respect to both nuclear and cytoplasmic genes (Nec and Nen, respectively). Compared to hermaphroditism, gynodioecy generally reduces effective population sizes for both kinds of loci to an extent depending on the frequency of females, the sex determination system, and the selfing rate of hermaphrodites. This reduction is due to fitness differences between the sexes and is highly influenced by the mode of inheritance of this fitness. In absence of selfing, nuclear gynodioecy results in a reduction of Nec that depends strongly on the dominance of male sterility alleles, while Nen remains equal to the census number (N). With cytonuclear gynodioecy, both cytoplasmic and nuclear effective sizes are reduced, and at the extreme, dioecy results in the minimum Nec values and either minimum or maximum Nen values (for low or high frequency of females, respectively). When selfing occurs, gynodioecy either increases or decreases Nen as compared to hermaphroditism with the same selfing rate of hermaphrodites. Unexpectedly, Nec also varies with the selfing rate. Thus the genetic sex-determination system appears as a major factor for the nuclear and cytoplasmic genetic diversities of gynodioecious species.

Karyotype of the South African katydid Hetrodes pupus (Linnaeus, 1758) (Orthoptera, Tettigoniidae) with special reference to relationships within the Hetrodinae subfamily

Zootaxa ◽  
2009 ◽  
Vol 2137 (1) ◽  
pp. 43-50 ◽  
Author(s):  
ELŻBIETA WARCHAŁOWSKA-ŚLIWA ◽  
ALEXANDER G. BUGROV
Keyword(s):  
Comparative Analysis ◽  
Sex Determination ◽  
Special Reference ◽  
South African ◽  
X Chromosome ◽  
Chromosome Evolution ◽  
Cytogenetic Study ◽  
Meiotic Chromosomes ◽  
Determination System ◽  
Sex Determination System

The taxonomic position of Hetrodes pupus (Tettigoniidae, Hetrodinae) was clarified by a cytogenetic study of mitotic and meiotic chromosomes, including the localization of heterochromatin by C-banding. The karyotype of this species consists of 26 acrocentric autosomes and an acrocentric X chromosome, the largest element of the karyotype (2n male=27, FN=27; sex determination system is X0 male/XX female). A cytogenetic comparative analysis of the Hetrodinae and other katydids revealed (1) the similarity of the karyotypic features of Hetrodinae and Microtettigoninae, indicating monophyly; (2) that the morphology of the Hetrodinae karyotype is the result of parallel chromosome evolution via a decrease in the number of chromosome arms (FN).

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.

The Genome Size of Some Species of Hyalomma Ticks from Turkish Thrace 

2018 ◽  
Vol 23 (11) ◽  
pp. 2122 ◽  
Author(s):  
Nadim Yılmazer
Keyword(s):  
Genome Size ◽  
X Chromosome ◽  
Tick Species ◽  
Animal Health ◽  
Chromosome Size ◽  
Diploid Genome ◽  
Flow Cytometric ◽  
Determination System ◽  
Sex Determination System ◽  
First Time

Hyalomma scupense, H. excavatum and H. marginatum are globally important tick species, as well as in Turkey, both in terms of human and animal health. The genome sizes of these tick species were determined in this study for the first time. From flow cytometric measurements, diploid genome sizes of female and male H. scupense were found to be 2.13 pg and 1.75 pg, respectively, while H. excavatum were 2.21 pg and 1.94 pg, and H. marginatum were 2.48 pg and 1.98 pg, respectively. Differences in diploid genome size indicate X chromosome size of females and males in these ticks because they have an XX:XO sex determination system. Thus, it was estimated that the X chromosome of H. scupense, H. excavatum, and H. marginatum may be composed of as much as 0.38 pg, 0.27 pg, and 0.50 pg of DNA, respectively. These findings indicate suitability of these three species for genome sequencing due to the relatively small size of their genomes compared with other tick species.

scholarly journals Restricted X chromosome introgression and support for Haldane's rule in hybridizing damselflies

2021 ◽  
Author(s):  
Janne Swaegers ◽  
Rosa Ana Sanchez-Guillen ◽  
Pallavi Chauhan ◽  
Maren Wellenreuther ◽  
Bengt Hansson
Keyword(s):  
X Chromosome ◽  
Sex Chromosomes ◽  
Hybrid Zones ◽  
Haldane’S Rule ◽  
Haldane's Rule ◽  
Genome Wide ◽  
Determination System ◽  
Heterogametic Sex ◽  
Sex Determination System ◽  
Genomic Introgression

Contemporary hybrid zones act as natural laboratories for the investigation of species boundaries and allow to shed light on the little understood roles of sex chromosomes in species divergence. Sex chromosomes are considered to function as a hotspot of genetic divergence between species; indicated by less genomic introgression compared to autosomes during hybridisation. Moreover, they are thought to contribute to Haldane's rule which states that hybrids of the heterogametic sex are more likely to be inviable or sterile. To test these hypotheses, we used contemporary hybrid zones of Ischnura elegans, a damselfly species that has been expanding its range into the northern and western regions of Spain, leading to chronic hybridization with its sister species Ischnura graellsii. We analysed genome-wide SNPs in the Spanish I. elegans and I. graellsii hybrid zone and found (i) that the X chromosome shows less genomic introgression compared to autosomes and (ii) that males are underrepresented among admixed individuals as predicted by Haldane's rule. This is the first study in Odonata that suggests a role of the X chromosome in reproductive isolation. Moreover, our data adds to the few studies on species with X0 sex determination system and contradicts the hypothesis that the absence of a Y chromosome causes exceptions to Haldane's rule.

scholarly journals A 180 Myr-old female-specific genome region in sturgeon reveals the oldest known vertebrate sex determining system with undifferentiated sex chromosomes

2021 ◽  
Vol 376 (1832) ◽  
pp. 20200089
Author(s):  
Heiner Kuhl ◽  
Yann Guiguen ◽  
Christin Höhne ◽  
Eva Kreuz ◽  
Kang Du ◽  
...  
Keyword(s):  
Sex Determination ◽  
Sex Chromosomes ◽  
Sex Chromosome ◽  
Specific Sequence ◽  
Genome Region ◽  
Acipenser Ruthenus ◽  
Determination System ◽  
Sex Determination System ◽  
Female Specific ◽  
Polyploidization Event

Several hypotheses explain the prevalence of undifferentiated sex chromosomes in poikilothermic vertebrates. Turnovers change the master sex determination gene, the sex chromosome or the sex determination system (e.g. XY to WZ). Jumping master genes stay main triggers but translocate to other chromosomes. Occasional recombination (e.g. in sex-reversed females) prevents sex chromosome degeneration. Recent research has uncovered conserved heteromorphic or even homomorphic sex chromosomes in several clades of non-avian and non-mammalian vertebrates. Sex determination in sturgeons (Acipenseridae) has been a long-standing basic biological question, linked to economical demands by the caviar-producing aquaculture. Here, we report the discovery of a sex-specific sequence from sterlet ( Acipenser ruthenus ). Using chromosome-scale assemblies and pool-sequencing, we first identified an approximately 16 kb female-specific region. We developed a PCR-genotyping test, yielding female-specific products in six species, spanning the entire phylogeny with the most divergent extant lineages ( A. sturio, A. oxyrinchus versus A. ruthenus, Huso huso ), stemming from an ancient tetraploidization. Similar results were obtained in two octoploid species ( A. gueldenstaedtii, A. baerii ). Conservation of a female-specific sequence for a long period, representing 180 Myr of sturgeon evolution, and across at least one polyploidization event, raises many interesting biological questions. We discuss a conserved undifferentiated sex chromosome system with a ZZ/ZW-mode of sex determination and potential alternatives. This article is part of the theme issue ‘Challenging the paradigm in sex chromosome evolution: empirical and theoretical insights with a focus on vertebrates (Part I)’.

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