The structure of the Xyp sex chromosome complex in male meiosis of two beetles: Tenebrio molitor (Tenebrionidae) and Chrysolina graminis (Chrysomelidae)

1997 ◽  
Vol 53 (2) ◽  
pp. 162-167 ◽  
Author(s):  
K. W. Wolf
Keyword(s):  
Sex Chromosome ◽  
Tenebrio Molitor ◽  
Male Meiosis

scholarly journals polo, a mitotic mutant of Drosophila displaying abnormal spindle poles

1988 ◽  
Vol 89 (1) ◽  
pp. 25-38 ◽  
Author(s):  
C.E. Sunkel ◽  
D.M. Glover
Keyword(s):  
High Frequency ◽  
Sex Chromosome ◽  
Living Cells ◽  
Male Meiosis ◽  
Mitotic Spindles ◽  
Spindle Poles ◽  
Immunofluorescence Studies ◽  
Meiotic Spindles ◽  
Circular Arrangement ◽  
Chromosome Disjunction

Neuroblast cells in larvae homozygous for mutant alleles of the locus polo show a high frequency of metaphases in which the chromosomes have a circular arrangement, and anaphase figures in which chromosomes appear to be randomly oriented with respect to at least one of the spindle poles. These defects appear to lead to the production of polyploid cells. Sex chromosome disjunction is affected in male meiosis, primarily in the second division, and the meiotic spindles of living cells are abnormal. One allele is a larval lethal, whereas another is semi-lethal with about 7% of homozygotes surviving as adults. Embryos from homozygous polo females have aberrant mitotic spindles that are highly branched and have broad poles. Immunofluorescence studies with an antibody that recognizes an antigen associated with the centrosome indicate that the organization of this organelle is disrupted in the mutant embryos.

scholarly journals Sexually dimorphic recombination can facilitate the establishment of sexually antagonistic polymorphisms in guppies

2018 ◽  
Author(s):  
Roberta Bergero ◽  
Jim Gardner ◽  
Beth Bader ◽  
Lengxob Yong ◽  
Deborah Charlesworth
Keyword(s):  
Sex Chromosomes ◽  
Poecilia Reticulata ◽  
Common Ancestor ◽  
Sex Chromosome ◽  
Empirical Support ◽  
Male Meiosis ◽  
Sexually Dimorphic ◽  
Sex Linkage ◽  
Recombination Suppression ◽  
Males And Females

Summary/AbstractRecombination suppression between sex chromosomes is often stated to evolve in response to polymorphisms for mutations that affect fitness of males and females in opposite directions (sexually antagonistic, or SA, mutations), but direct empirical support is lacking. The sex chromosomes of the fish Poecilia reticulata (the guppy) carry SA polymorphisms, making them excellent for testing this hypothesis for the evolution of sex linkage. We resequenced genomes of male and female guppies and, unexpectedly, found that variants on the sex chromosome indicate no extensive region with fully sex-linked genotypes, though many variants show strong evidence for partial sex linkage. We present genetic mapping results that help understand the evolution of the guppy sex chromosome pair. We find very different distributions of crossing over in the two sexes, with recombination events in male meiosis detected only at the tips of the chromosomes. The guppy may exemplify a route for sex chromosome evolution in which low recombination in males, likely evolved in a common ancestor, has facilitated the establishment of sexually antagonistic polymorphisms.

scholarly journals Involvement of synaptonemal complex proteins in sex chromosome segregation during marsupial male meiosis

PLoS Genetics ◽  
2005 ◽  
Vol preprint (2006) ◽  
pp. e136
Author(s):  
Jesus Page ◽  
Alberto Viera ◽  
Maria Teresa Parra ◽  
Roberto de la Fuente ◽  
Jose A. Suja ◽  
...  
Keyword(s):  
Synaptonemal Complex ◽  
Chromosome Segregation ◽  
Sex Chromosome ◽  
Male Meiosis

Unusual sex chromosome inheritance in mammals

1970 ◽  
Vol 259 (828) ◽  
pp. 15-36 ◽  
Keyword(s):  
Sex Determination ◽  
Sex Chromosomes ◽  
Sex Chromosome ◽  
General Pattern ◽  
Male Meiosis ◽  
Present Knowledge ◽  
Microtus Arvalis ◽  
Present Contribution ◽  
Original Size ◽  
Heterogametic Sex

The male has proven to be the heterogametic sex in all mammals studied so far. As is well known, the males usually have the sex chromosomes XY and the females XX. In recent years, however, many exceptions from this general pattern have been discovered. With our present knowledge, the different sex chromosome mechanisms in mammals may be divided into five main groups, and the first of them into subgroups, as follows: (i) Species with XX/XY sex chromosomes: (a) X of original size (see below), Y small; (b) X large, Y small; (c) X large, Y large: (i) end-to-end association of X and Y at male meiosis, (ii) chiasma between X and Y at male meiosis. (ii) Species with XX/XY 1 Y 2 sex chromosomes. (iii) Species with X 1 X 1 X 2 X 2 /X 1 X 2 Y sex chromosomes. (iv) Species with complicated or unknown mechanisms for sex determination. (v) Species with mosaicism of the sex chromosomes, but apparently with an XX/XY mechanism for sex determination. The present contribution will mainly deal with unusual sex chromosome inheritance, that is the groups (ii), (iii) and (iv) above, but the other two groups will also be briefly discussed and examples will be given. Recently Raicu, Kirillova & Hamar (1969) described a new sex chromosome mechanism ( X 1 X 1 X 2 X 2 /X 1 X 2 Y 1 Y 2 ) in the vole Microtus arvalis , but this observation was not confirmed by Schmid (1969), who found an ordinary XX/XY mechanism with both X and Y readily identifiable and of ‘normal’ size, the X comprising 5.6% of ( n A + X) and Y being the smallest chromosome of the complement. Late DNA replication was demonstrated in the allocyclic X and in the Y. Also Wolf (1969) found normal sex chromosomes in this species with no multivalents at male meiosis.

scholarly journals Isolation and Cytogenetic Characterization of Male Meiotic Mutants of Drosophila melanogaster

Genetics ◽  
2004 ◽  
Vol 166 (4) ◽  
pp. 1795-1806
Author(s):  
Kazuyuki Hirai ◽  
Satomi Toyohira ◽  
Takashi Ohsako ◽  
Masa-Toshi Yamamoto
Keyword(s):  
Drosophila Melanogaster ◽  
Sex Chromosome ◽  
Male Meiosis ◽  
Fourth Chromosome ◽  
Homologous Chromosomes ◽  
Meiotic Mutants ◽  
Chromatid Cohesion ◽  
Cytogenetic Characterization ◽  
Meiosis I

Abstract Proper segregation of homologous chromosomes in meiosis I is ensured by pairing of homologs and maintenance of sister chromatid cohesion. In male Drosophila melanogaster, meiosis is achiasmatic and homologs pair at limited chromosome regions called pairing sites. We screened for male meiotic mutants to identify genes required for normal pairing and disjunction of homologs. Nondisjunction of the sex and the fourth chromosomes in male meiosis was scored as a mutant phenotype. We screened 2306 mutagenized and 226 natural population-derived second and third chromosomes and obtained seven mutants representing different loci on the second chromosome and one on the third. Five mutants showed relatively mild effects (<10% nondisjunction). mei(2)yh149 and mei(2)yoh7134 affected both the sex and the fourth chromosomes, mei(2)yh217 produced possible sex chromosome-specific nondisjunction, and mei(2)yh15 and mei(2)yh137 produced fourth chromosome-specific nondisjunction. mei(2)yh137 was allelic to the teflon gene required for autosomal pairing. Three mutants exhibited severe defects, producing >10% nondisjunction of the sex and/or the fourth chromosomes. mei(2)ys91 (a new allele of the orientation disruptor gene) and mei(3)M20 induced precocious separation of sister chromatids as early as prometaphase I. mei(2)yh92 predominantly induced nondisjunction at meiosis I that appeared to be the consequence of failure of the separation of paired homologous chromosomes.

scholarly journals Sex chromosome pairing mediated by euchromatic homology in Drosophila male meiosis

2019 ◽  
Author(s):  
Christopher A. Hylton ◽  
Katie Hansen ◽  
Andrew Bourgeois ◽  
John E. Tomkiel
Keyword(s):  
Sex Chromosomes ◽  
Sex Chromosome ◽  
Intergenic Spacer ◽  
Male Meiosis ◽  
Early Prophase ◽  
Dna Breaks ◽  
Late Prophase ◽  
Prophase I ◽  
Y Chromosomes ◽  
Meiosis I

ABSTRACTTo maintain proper ploidy, haploid sex cells must undergo two subsequent meiotic divisions. During meiosis I, homologs pair and remain conjoined until segregation at anaphase. Drosophila melanogaster spermatocytes are unique in that the canonical events of meiosis I including synaptonemal complex (SC) formation, double-strand DNA breaks, and chiasmata are absent. Sex chromosomes pair at intergenic spacer sequences within the heterochromatic rDNA while euchromatin is required to pair and segregate autosomal homologies, suggesting that pairing may be limited to specific sequences. However, previous work generated from genetic segregation assays or observations of late prophase I/prometaphase I chromosome associations fail to differentiate pairing from conjunction. Here, we separately examined the capability of X euchromatin to pair and conjoin using an rDNA-deficient X and a series of Dp(1;Y) chromosomes. Genetic assays showed that duplicated X euchromatin can substitute for endogenous rDNA pairing sites. Segregation was not proportional to homology length, and pairing could be mapped to nonoverlapping sequences within a single Dp(1;Y). Using fluorescent in situ hybridization (FISH) to early prophase I spermatocytes, we showed that pairing occurred with high fidelity at all homologies tested. Pairing was unaffected by the presence of X rDNA, nor could it be explained by rDNA magnification. By comparing genetic and cytological data, we determined that centromere proximal pairings were best at segregation. Segregation was dependent on the conjunction protein Stromalin in Meiosis while the autosomal-specific Teflon was dispensable. Overall, our results suggest that pairing may occur at all homologies, but there may be sequence or positional requirements for conjunction.ARTICLE SUMMARYDrosophila males have evolved a unique system of chromosome segregation in meiosis that lacks recombination. Chromosomes pair at selected sequences suggesting that early steps of meiosis may also differ in this organism. Using Y chromosomes carrying portions of X material, we show that pairing between sex chromosomes can be mediated by sequences other than the previously identified rDNA pairing sites. We propose that pairing may simply be homology-based and may not differ from canonical meiosis observed in females. The main difference in males may be that conjunctive mechanisms that join homologs in the absence of crossovers.

Heterochromatin characterization and ribosomal gene location in two monotypic genera of bloodsucker bugs (Cimicidae, Heteroptera) with holokinetic chromosomes and achiasmatic male meiosis

2014 ◽  
Vol 104 (6) ◽  
pp. 788-793 ◽  
Author(s):  
M.G. Poggio ◽  
O. Di Iorio ◽  
P. Turienzo ◽  
A. G. Papeschi ◽  
M.J. Bressa
Keyword(s):  
Central Region ◽  
Sex Chromosome ◽  
Male Meiosis ◽  
Ribosomal Gene ◽  
Nucleolus Organizer ◽  
Gene Location ◽  
Holokinetic Chromosomes ◽  
Small Areas ◽  
Nucleolus Organizer Regions ◽  
Autosomal Pair

AbstractMembers of the family Cimicidae (Heteroptera: Cimicomorpha) are temporary bloodsuckers on birds and bats as primary hosts and humans as secondary hosts.Acanthocrios furnarii(2n=12=10+XY, male) andPsitticimex uritui(2n=31=28+X1X2Y, male) are two monotypic genera of the subfamily Haematosiphoninae, which have achiasmatic male meiosis of collochore type. Here, we examined chromatin organization and constitution of cimicid holokinetic chromosomes by determining the amount, composition and distribution of constitutive heterochromatin, and number and location of nucleolus organizer regions (NORs) in both species. Results showed that these two bloodsucker bugs possess high heterochromatin content and have an achiasmatic male meiosis, in which three regions can be differentiated in each autosomal bivalent: (i) terminal heterochromatic regions in repulsion; (ii) a central region, where the homologous chromosomes are located parallel but without contact between them; and (iii) small areas within the central region, where collochores are detected.Acanthocrios furnariipresented a single NOR on an autosomal pair, whereasP. urituipresented two NORs, one on an autosomal pair and the other on a sex chromosome. All NORs were found to be associated with CMA3bright bands, indicating that the whole rDNA repeating unit is rich in G+C base pairs. Based on the variations in the diploid autosomal number, the presence of simple and multiple sex chromosome systems, and the number and location of 18S rDNA loci in the two Cimicidae species studied, we might infer that rDNA clusters and genome are highly dynamic among the representatives of this family.

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