scholarly journals Meiotic mutants that cause a polar decrease in recombination on the X chromosome in Caenorhabditis elegans.

Genetics ◽  
1994 ◽  
Vol 136 (1) ◽  
pp. 119-127
Author(s):  
S A Broverman ◽  
P M Meneely
Keyword(s):  
Caenorhabditis Elegans ◽  
Genetic Map ◽  
X Chromosome ◽  
Recessive Mutations ◽  
Feature Characteristic ◽  
Comparable Effect ◽  
Chromosome Recombination ◽  
The Right ◽  
Chromosome Nondisjunction ◽  
Pairing Region

Abstract Recessive mutations in three autosomal genes, him-1, him-5 and him-8, cause high levels of X chromosome nondisjunction in hermaphrodites of Caenorhabditis elegans, with no comparable effect on autosomal disjunction. Each of the mutants has reduced levels of X chromosome recombination, correlating with the increase in nondisjunction. However, normal or elevated levels of recombination occur at the end of the X chromosome hypothesized to contain the pairing region (the left end), with recombination levels decreasing in regions approaching the right end. Thus, both the number and the distribution of X chromosome exchange events are altered in these mutants. As a result, the genetic map of the X chromosome in the him mutants exhibits a clustering of genes due to reduced recombination, a feature characteristic of the genetic map of the autosomes in non-mutant animals. We hypothesize that these him genes are needed for some processive event that initiates near the left end of the X chromosome.

scholarly journals pag-3, a Caenorhabditis elegans Gene Involved in Touch Neuron Gene Expression and Coordinated Movement

Genetics ◽  
1996 ◽  
Vol 142 (1) ◽  
pp. 141-147 ◽  
Author(s):  
Yiwen Jia ◽  
Guofeng Xie ◽  
Eric Aamodt
Keyword(s):  
Gene Expression ◽  
Caenorhabditis Elegans ◽  
X Chromosome ◽  
Ectopic Expression ◽  
Immunofluorescence Staining ◽  
Wild Type ◽  
Recessive Mutations ◽  
The Right ◽  
Three Factor

Mutations in a newly identified gene, pag-3, cause ectopic expression of touch neuron genes mec-7, mec-7lacZ and mec-4lacZ in the lineal sisters of the ALM touch neurons, the BDU neurons. pag-3 mutants also show a reverse kinker uncoordinated phenotype. The first pag-3 allele was isolated in a screen for mutants with altered immunofluorescence staining patterns. Two additional pag-3 alleles were identified in a noncomplementation screen of 38,000 haploid genomes. All of the pag-3 alleles were recessive to wild type and cause the same phenotypes. Two-factor crosses, deficiency mapping and three-factor crosses located pag-3 to the right arm of the X chromosome between unc-3 and unc-7. Because recessive mutations in pag-3 result in expression of several touch cell specific genes in the BDU neurons, pag-3(+) must directly or indirectly suppress expression of these genes in the BDU neurons. Although pag-3 mutants did not show mec-3lacZ expression in their BDU neurons, expression of mec-7lacZ and mec-4lacZ in the BDU neurons of pag-3 mutants required mec-3(+).

scholarly journals MORE SEX-DETERMINATION MUTANTS OF CAENORHABDITIS ELEGANS

Genetics ◽  
1980 ◽  
Vol 96 (3) ◽  
pp. 649-664 ◽  
Author(s):  
Jonathan Hodgkin
Keyword(s):  
Caenorhabditis Elegans ◽  
Sex Determination ◽  
X Chromosome ◽  
Constitutive Expression ◽  
Complementation Group ◽  
Sperm Production ◽  
Recessive Mutations ◽  
Her 2 ◽  
Map Location ◽  
Her Genes

ABSTRACT Sex determination in Caenorhabditis elegans is controlled by the X chromosome: autosome ratio, i.e. 2A;XX animals are hermaphrodite, and 2A;XO animals are male. A procedure for isolating 2A;XO animals that are transformed into hermaphrodites has been developed. Nine mutations causing this transformation have been obtained: eight are recessive, and all of these fall into a new autosomal complementation group, her-1 V. The remaining mutation (her-2) is dominant and has a genetic map location similar to that of tra-1 III. Recessive mutations of tra-1 cause the reverse transformation, transforming 2A;XX animals into males. Therefore, the her-2 mutation may result in constitutive expression of tra-1. Mutations in her-1 are without effect on XX animals, but the her-2 mutation prevents sperm production in both XX and XO animals, in addition to its effect on the sexual phenotype of XO animals. The epistatic relationships between tra and her genes are used to deduce a model for the action of these genes in controlling sex determination.

Genetic Analysis of X-Chromosome Dosage Compensation in Caenorhabditis elegans

Genetics ◽  
1987 ◽  
Vol 117 (1) ◽  
pp. 25-41
Author(s):  
Philip M Meneely ◽  
William B Wood
Keyword(s):  
Caenorhabditis Elegans ◽  
Genetic Analysis ◽  
X Chromosome ◽  
Dosage Compensation ◽  
Normal Function ◽  
Complete Loss ◽  
Loss Of Function ◽  
Recessive Mutations ◽  
Genetic Assay

ABSTRACT We have shown that the phenotypes resulting from hypomorphic mutations (causing reduction but not complete loss of function) in two X-linked genes can be used as a genetic assay for X-chromosome dosage compensation in Caenorhabditis elegans between males (XO) and hermaphrodites (XX). In addition we show that recessive mutations in two autosomal genes, dpy-21 V and dpy-26 IV, suppress the phenotypes resulting from the X-linked hypomorphic mutations, but not the phenotypes resulting from comparable autosomal hypomorphic mutations. This result strongly suggests that the dpy-21 and dpy-26 mutations cause increased X expression, implying that the normal function of these genes may be to lower the expression of X-linked genes. Recessive mutations in two other dpy genes, dpy-22 X and dpy-23 X, increase the severity of phenotypes resulting from some X-linked hypomorphic mutations, although dpy-23 may affect the phenotypes resulting from the autosomal hypomorphs as well. The mutations in all four of the dpy genes show their effects in both XO and XX animals, although to different degrees. Mutations in 18 other dpy genes do not show these effects.

RADIATION-SENSITIVE MUTANTS OF CAENORHABDITIS ELEGANS

Genetics ◽  
1982 ◽  
Vol 102 (2) ◽  
pp. 159-178
Author(s):  
Philip S Hartman ◽  
Robert K Herman
Keyword(s):  
Caenorhabditis Elegans ◽  
X Chromosome ◽  
Spontaneous Mutation ◽  
Radiation Sensitivity ◽  
Temperature Sensitive ◽  
X Rays ◽  
C Elegans ◽  
Elevated Frequency ◽  
Rad Mutants ◽  
Chromosome Nondisjunction

ABSTRACT Nine rad (for abnormal radiation sensitivity) mutants hypersensitive to ultraviolet light were isolated in the small nematode Caenorhabditis elegans. The mutations are recessive to their wild-type alleles, map to four of the six linkage groups in C. elegans and define nine new games named rad-1 through rad-9. Two of the mutants—rad-1 and rad-2—are very hypersensitive to X rays, and three—rad-2, rad-3 and rad-4—are hypersensitive to methyl methanesulfonate under particular conditions of exposure. The hypersensitivity of these mutants to more than one DNA-damaging agent suggests that they may be abnormal in DNA repair. One mutant—rad-5, a temperature-sensitive sterile mutant—shows an elevated frequency of spontaneous mutation at more than one locus; rad-4, which shows a cold-sensitive embryogenesis, reduces meiotic X-chromosome nondisjunction tenfold and partially suppresses some but not all mutations that increase meiotic X-chromosome nondisjunction; the viability of rad-6 hermaphrodites is half that of rad-6 males at 25°; and newly mature (but not older) rad-8 hermaphrodites produce many inviable embryo progeny. Meiotic recombination frequencies were measured for seven rad mutants and found to be close to normal.

scholarly journals The Caenorhabditis elegans Dosage Compensation Machinery Is Recruited to X Chromosome DNA Attached to an Autosome

Genetics ◽  
2000 ◽  
Vol 156 (4) ◽  
pp. 1603-1621
Author(s):  
Jason D Lieb ◽  
Carlos Ortiz de Solorzano ◽  
Enrique Garcia Rodriguez ◽  
Arthur Jones ◽  
Michael Angelo ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
X Chromosome ◽  
Dosage Compensation ◽  
Dna Sequences ◽  
Three Dimensional ◽  
Dosage Compensation Complex ◽  
X Chromosomes ◽  
Cis Acting ◽  
Recognition Elements ◽  
The Right

Abstract The dosage compensation machinery of Caenorhabditis elegans is targeted specifically to the X chromosomes of hermaphrodites (XX) to reduce gene expression by half. Many of the trans-acting factors that direct the dosage compensation machinery to X have been identified, but none of the proposed cis-acting X chromosome-recognition elements needed to recruit dosage compensation components have been found. To study X chromosome recognition, we explored whether portions of an X chromosome attached to an autosome are competent to bind the C. elegans dosage compensation complex (DCC). To do so, we devised a three-dimensional in situ approach that allowed us to compare the volume, position, and number of chromosomal and subchromosomal bodies bound by the dosage compensation machinery in wild-type XX nuclei and XX nuclei carrying an X duplication. The dosage compensation complex was found to associate with a duplication of the right 30% of X, but the complex did not spread onto adjacent autosomal sequences. This result indicates that all the information required to specify X chromosome identity resides on the duplication and that the dosage compensation machinery can localize to a site distinct from the full-length hermaphrodite X chromosome. In contrast, smaller duplications of other regions of X appeared to not support localization of the DCC. In a separate effort to identify cis-acting X recognition elements, we used a computational approach to analyze genomic DNA sequences for the presence of short motifs that were abundant and overrepresented on X relative to autosomes. Fourteen families of X-enriched motifs were discovered and mapped onto the X chromosome.

scholarly journals Natural variations in reproductive aging phenotypes reveal the importance of early reproductive period in Caenorhabditis elegans

2021 ◽  
Author(s):  
Jiseon Lim ◽  
Jun Kim ◽  
Junho Lee
Keyword(s):  
Caenorhabditis Elegans ◽  
X Chromosome ◽  
Brood Size ◽  
Current Knowledge ◽  
Reproductive Capacity ◽  
Initial Population ◽  
Reproductive Aging ◽  
C Elegans ◽  
Wild Strains ◽  
Chromosome Nondisjunction

Although reproductive capacity is a major factor in individual fitness, aging of the reproductive system precedes somatic aging and may reduce the total brood size. Genetic studies have led to the development of a body of evolutionary theory in the nematode Caenorhabditis elegans, but these studies did not take into account current knowledge about the natural history of C. elegans. To enhance our understanding of reproductive aging in C. elegans, we measured and compared two reproductive aging-related traitsthe number of progeny and the X-chromosome nondisjunction rateof 96 wild strains during early, late and total reproductive periods. We found that the two traits exhibited natural phenotypic variation, with few outliers, and that the brood size and the X-chromosome nondisjunction rate were not genetically correlated. Contrary to a previous hypothesis, that reproductive aging contributes to the generation of an optimal total number of offspring, we found that the total brood size did not converge to an optimal value, and early brood size was more constant than total brood size among wild strains. We speculate that reproductive aging is a by-product of a rapid increase in the initial population size, which might be related to the boom-and-bust lifestyle of C. elegans. We also identified loci and candidate genetic variants significantly associated with X-chromosome nondisjunction rate in the late and total reproductive periods. Our results provide an insight into reproductive aging in wild C. elegans strains.

DOMINANT X-CHROMOSOME NONDISJUNCTION MUTANTS OF CAENORHABDITIS ELEGANS

Genetics ◽  
1982 ◽  
Vol 102 (3) ◽  
pp. 379-400
Author(s):  
Robert K Herman ◽  
Claire K Kari ◽  
Philip S Hartman
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Caenorhabditis Elegans ◽  
X Chromosome ◽  
Primary Structure ◽  
Yeast Saccharomyces Cerevisiae ◽  
Group Iii ◽  
Specific Suppression ◽  
Allele Specific ◽  
Insertion Mutations ◽  
Chromosome Nondisjunction

ABSTRACT Two classes of frameshift suppressors distributed at 22 different loci were identified in previous studies in the yeast Saccharomyces cerevisiae. These suppressors exhibited allele-specific suppression of +1 G:C insertion mutations in either glycine or proline codons, designated as group II and group III frameshift mutations, respectively. Genes corresponding to representative suppressors of each group have been shown to encode altered glycine or proline tRNAs containing four base anticodons.—This communication reports the existence of a third class of frameshift suppressor that exhibits a wider range in specificity of suppression. The suppressors map at three loci, suf12, suf13, and suf14, which are located on chromosomes IV, XV, and XIV, respectively. The phenotypes of these suppressors suggest that suppression may be mediated by genes other than those encoding the primary structure of glycine or proline tRNAs.

scholarly journals Recombination between small X chromosome duplications and the X chromosome in Caenorhabditis elegans.

Genetics ◽  
1989 ◽  
Vol 121 (4) ◽  
pp. 723-737
Author(s):  
R K Herman ◽  
C K Kari
Keyword(s):  
Caenorhabditis Elegans ◽  
X Chromosome ◽  
Chromosome Pairing ◽  
Meiotic Chromosome ◽  
Wild Type ◽  
X Chromosomes ◽  
Meiotic Chromosome Pairing ◽  
Small X ◽  
The One ◽  
The Right

Abstract Twelve new X chromosome duplications were identified and characterized. Eight are translocated to autosomal sites near four different telomeres, and four are free. Ten include unc-1(+), which in wild type is near the left end of the X chromosome, and two of these, mnDp72(X;IV) and mnDp73(X;f), extend rightward past dpy-3. Both mnDp72 and mnDp73 recombined with the one X chromosome in males in the unc-1-dpy-3 interval at a frequency 15- to 30-fold higher than was observed for X-X recombination in hermaphrodites in the same interval. Recombinant duplications and recombinant X chromosomes were both recovered. Recombination with the X chromosome in the unc-1-dpy-3 interval was also detected for five other unc-1(+) duplications, even though their right breakpoints lie within the interval. In hermaphrodites, mnDp72 and mnDp73 promoted meiotic X nondisjunction and recombined with an X chromosome in the unc-1-dpy-3 interval at frequencies comparable to that found for X-X recombination; mnDp72(X;IV) also promoted trisomy for chromosome IV. A mutation in him-8 IV was identified that severely reduced recombination between the two X chromosomes in hermaphrodites and between mnDp73 and the X chromosome in males. Recombination between the X chromosome and duplications of either the right end of the X or a region near but not including the left end was rare. We suggest that the X chromosome has one or more elements near its left end that promote meiotic chromosome pairing.

scholarly journals Natural variation in reproductive timing and X-chromosome nondisjunction in Caenorhabditis elegans

2021 ◽  
Author(s):  
Jiseon Lim ◽  
Jun Kim ◽  
Junho Lee
Keyword(s):  
Caenorhabditis Elegans ◽  
X Chromosome ◽  
Reproductive Timing ◽  
Male Production ◽  
C Elegans ◽  
In The Wild ◽  
Wild Strains ◽  
Large Brood ◽  
Insight Into ◽  
Chromosome Nondisjunction

Abstract Caenorhabditis elegans hermaphrodites first produce a limited number of sperm cells, before their germline switches to oogenesis. Production of progeny then ensues until sperm is depleted. Male production in the self-progeny of hermaphrodites occurs following X-chromosome nondisjunction during gametogenesis, and in the reference strain increases with age of the hermaphrodite parent. To enhance our understanding of the reproductive timecourse in C. elegans, we measured and compared progeny production and male proportion during the early and late reproductive periods of hermaphrodites for 96 wild C. elegans strains. We found that the two traits exhibited natural phenotypic variation with few outliers and a similar reproductive timing pattern as previous reports. Progeny number and male proportion were not correlated in the wild strains, implying that wild strains with a large brood size did not produce males at a higher rate. We also identified loci and candidate genetic variants significantly associated with male-production rate in the late and total reproductive periods. Our results provide an insight into life-history traits in wild C. elegans strains.

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