scholarly journals CHROMOSOME SEGREGATION INFLUENCED BY TWO ALLELES OF THE MEIOTIC MUTANT c(3)G IN DROSOPHILA MELANOGASTER  1  2

Genetics ◽  
1972 ◽  
Vol 71 (3) ◽  
pp. 367-400
Author(s):  
Jeffrey C Hall
Keyword(s):  
Drosophila Melanogaster ◽  
Low Temperature ◽  
Chromosome Segregation ◽  
Meiotic Division ◽  
Centromeric Heterochromatin ◽  
Temperature Sensitive ◽  
Crossing Over ◽  
Fourth Chromosome ◽  
Chromosome Behavior ◽  
Chromosome Nondisjunction

Abstract c(3)G is a gene in Drosophila melanogaster defined by two independently isolated mutants on the third chromosome. When homozygous in females, the mutants—c(3)G  17 or c(3)G  68—result in the elimination of meiotic crossing over and a great increase in nondisjunction at the first meiotic division. The gametic frequency of X-, second-, or third-chromosome nondisjunction is approximately .3 in c(3)G  17  , and .4 in c(3)G  68  ; for the fourth chromosome, the frequency is .2 in c(3)G  17 and .3 in c(3)G  68  . These values are at least two hundred fold greater than for spontaneous nondisjunction, though not high enough to indicate that chromosomes are distributed at random to the first meiotic division poles. Chromosomes loss is inferred from an excess of nullo-exceptional over diplo-exceptional ova. Loss is more frequent in c(3)G  68. If c(3)G females mate at low temperature, crossing over is still absent, but nondisjunction is decreased. c(3)G  17 is more temperature sensitive than c(3)G  68  .—Nonhomologous chromosomes tend to undergo nondisjunction in the same meiotic cells in c(3)G. Moreover, there is substantial nonhomologous pairing involving the larger chromosomes of the genome, inferred from the tendency for nonhomologs to disjoin from each other. Nonhomologous segregation is not observed between chromosome 4 and any other chromosome. c(3)G  68 exhibits more nonhomologous segregation than does c(3)G  17  , and, for either allele, the degree of nonhomologous segregation is directly proportional to the similarity in length of the two nonhomologs being considered. The degree of nonhomologous segregation is increased at low temperature.—Heterozygosity for inversions tends to increase c(3)G-mediated nondisjunction, and to alter the patterns of nonhomologous segregations. The effects are observed even if the inversion does not disrupt centromeric heterochromatin, and even though the inversions do not change the lengths of the chromosomes involved. In XXY females, c(3)G  17 shows more separation of the two X’s from the Y chromo-some than does c(3)G  68  . Fourth-chromosome nondisjunction is increased by the presence of a Y chromosome in both kinds of mutant females. But in XXY;c(3)G females which are also heterozygous for an X inversion, frequencies of fourth-chromosome nondisjunction are little different from those in XX; c(3)G females, while the degrees of XX-from-Y disjunction are increased.—The chromosome behavior of the two alleles of c(3)G is readily rationalized by a model which assumes that c(3)G+ controls a stage of meiosis prior to synapsis and crossing over. If exchange is directly disrupted in c(3)G homozygotes, disjunctional consequences should be the same in c(3)G  17 and c(3)G  68  . They are not. If, however, c(3)G+ controls a precondition to crossing over—such as the association of homologous and nonhomologous chromosomes—then the two alleles could each abolish crossing over, but lead to different amounts and patterns of nondisjunction.

scholarly journals Genes Involved in Sister Chromatid Separation and Segregation in the Budding Yeast Saccharomyces cerevisiae

Genetics ◽  
2001 ◽  
Vol 159 (2) ◽  
pp. 453-470
Author(s):  
Sue Biggins ◽  
Needhi Bhalla ◽  
Amy Chang ◽  
Dana L Smith ◽  
Andrew W Murray
Keyword(s):  
Chromosome Segregation ◽  
Sister Chromatid ◽  
Mitotic Spindle ◽  
Budding Yeast ◽  
Temperature Sensitive ◽  
Chromosome Behavior ◽  
Yeast Saccharomyces Cerevisiae ◽  
Sister Chromatids ◽  
Marked Chromosome ◽  
Sister Chromatid Separation

Abstract Accurate chromosome segregation requires the precise coordination of events during the cell cycle. Replicated sister chromatids are held together while they are properly attached to and aligned by the mitotic spindle at metaphase. At anaphase, the links between sisters must be promptly dissolved to allow the mitotic spindle to rapidly separate them to opposite poles. To isolate genes involved in chromosome behavior during mitosis, we microscopically screened a temperature-sensitive collection of budding yeast mutants that contain a GFP-marked chromosome. Nine LOC (loss of cohesion) complementation groups that do not segregate sister chromatids at anaphase were identified. We cloned the corresponding genes and performed secondary tests to determine their function in chromosome behavior. We determined that three LOC genes, PDS1, ESP1, and YCS4, are required for sister chromatid separation and three other LOC genes, CSE4, IPL1, and SMT3, are required for chromosome segregation. We isolated alleles of two genes involved in splicing, PRP16 and PRP19, which impair α-tubulin synthesis thus preventing spindle assembly, as well as an allele of CDC7 that is defective in DNA replication. We also report an initial characterization of phenotypes associated with the SMT3/SUMO gene and the isolation of WSS1, a high-copy smt3 suppressor.

scholarly journals Elevated levels of expression associated with regions of the Drosophila genome that lack crossing over

2008 ◽  
Vol 4 (6) ◽  
pp. 758-761 ◽  
Author(s):  
Penelope R Haddrill ◽  
Fergal M Waldron ◽  
Brian Charlesworth
Keyword(s):  
Gene Expression ◽  
Drosophila Melanogaster ◽  
Molecular Evolution ◽  
Translational Efficiency ◽  
Crossing Over ◽  
Drosophila Genome ◽  
Deleterious Mutations ◽  
Fourth Chromosome ◽  
Genome Wide ◽  
Control Of Expression

The recombinational environment influences patterns of molecular evolution through the effects of Hill–Robertson interference. Here, we examine genome-wide patterns of gene expression with respect to recombinational environment in Drosophila melanogaster . We find that regions of the genome lacking crossing over exhibit elevated levels of expression, and this is most pronounced for genes on the entirely non-crossing over fourth chromosome. We find no evidence for differences in the patterns of gene expression between regions of high, intermediate and low crossover frequencies. These results suggest that, in the absence of crossing over, selection to maintain control of expression may be compromised, perhaps due to the accumulation of deleterious mutations in regulatory regions. Alternatively, higher gene expression may be evolving to compensate for defective protein products or reduced translational efficiency.

scholarly journals GENETICALLY INDUCED MITOTIC EXCHANGE IN THE HETEROCHROMATIN OF DROSOPHILA MELANOGASTER

Genetics ◽  
1981 ◽  
Vol 99 (3-4) ◽  
pp. 443-459
Author(s):  
Leonard G Robbins
Keyword(s):  
Drosophila Melanogaster ◽  
Temperature Sensitive ◽  
Chromosome Behavior ◽  
Ribosomal Cistrons ◽  
Y Chromosomes ◽  
Multiple Copies

ABSTRACT Multiple copies of the 18s and 28sribosomal RNA cistrons are present in both the Xand Y chromosomes of Drosophila melanogaster.Data are presented here that identify a locus, Rex,that causes exchange-like events between duplicated ribosomal complexes at the ends of an attached-XY chromosome. Rex:(1) is close to or in the basal heterochromatin of the Xchromosome; (2)is semidominant and (its effect) is temperature sensitive; (3) acts maternally; and (4) affects behavior of paternally derived attached-XY chromosomes shortly after fertilization. Though, at this point, the existence of Rexis known only from its effects on behavior of a particular compound chromosome, it presents intriguing possibilities for understanding regulation of chromosome behavior and organization of the ribosomal cistrons.

scholarly journals Population genetics of tandem repeats in centromeric heterochromatin: unequal crossing over and chromosomal divergence at the Responder locus of Drosophila melanogaster.

Genetics ◽  
1993 ◽  
Vol 135 (2) ◽  
pp. 477-487 ◽  
Author(s):  
E L Cabot ◽  
P Doshi ◽  
M L Wu ◽  
C I Wu
Keyword(s):  
Drosophila Melanogaster ◽  
Large Scale ◽  
Tandem Repeats ◽  
Evolutionary Dynamics ◽  
Repetitive Sequences ◽  
High Rate ◽  
Centromeric Heterochromatin ◽  
Crossing Over ◽  
Unequal Crossing Over ◽  
Left And Right

Abstract The Responder (Rsp) locus in Drosophila melanogaster is the target locus of segregation distortion and is known to be comprised of a tandem array of 120-bp repetitive sequences. In this study, we first determined the large scale molecular structure of the Rsp locus, which extends over a region of 600 kb on the standard sensitive (cn bw) chromosome. Within the region, small Rsp repeat arrays are interspersed with non-Rsp sequences and account for 10-20% of the total sequences. We isolated and sequenced 32 Rsp clones from three different chromosomes. The main results are: (1) Rsp repeats isolated from the same chromosome are not more similar than those from different chromosomes. This implies either that there are more homologous exchanges at the Rsp locus than expected or, alternatively, that the second chromosomes of D. melanogaster have diverged from one another more recently at the centromeric heterochromatin than at the nearby euchromatin. (2) The repeats usually have a dimeric structure with an average difference of 16% between the left and right halves. The differences allow us to easily identify the products of unequal exchanges. Despite the large differences between the two halves, exchanges have occurred frequently and the majority of them fall within a 29-bp interval of identity between the two halves. Our data thus support the suggestion that recombination depends on short stretches of complete identity rather than long stretches of general homology. (3) Frequent unequal crossover events obscure the phylogenetic relationships between repeats; therefore, different parts of any single repeat could often have different phylogenetic histories. The high rate of unequal crossing over may also help explain the evolutionary dynamics of the Rsp locus.

scholarly journals THE EFFECT OF RECOMBINATION-DEFECTIVE MEIOTIC MUTANTS ON FOURTH-CHROMOSOME CROSSING OVER IN DROSOPHILA MELANOGASTER

Genetics ◽  
1978 ◽  
Vol 90 (4) ◽  
pp. 699-712
Author(s):  
L Sandler ◽  
Paul Szauter
Keyword(s):  
Drosophila Melanogaster ◽  
Spatial Distribution ◽  
The Other ◽  
Crossing Over ◽  
Chromosome 4 ◽  
Wild Type ◽  
Fourth Chromosome ◽  
Meiotic Mutants ◽  
Other Hand

ABSTRACT Crossing over was measured on the normally achiasmate fourth chromosome in females homozygous for one of our different recombination-defective meiotic mutants. Under the influence of those meiotic mutants that affect the major chromosomes by altering the spatial distribution of exchanges, meiotic fourth-chromosome recombinants were recovered irrespective of whether or not the meiotic mutant decreases crossing over on the other chromosomes. No crossing over, on the other hand, was detected on chromosome 4 in either wild type or in the presence of a meiotic mutant that decreases the frequency, but that does not affect the spatial distribution, of exchange on the major chromosomes. It is concluded from these observations that (a) in wild type there are regional constraints on exchange that can be attenuated or eliminated by the defects caused by recombination-defective meiotic mutants; (b) these very constraints account for the absence of recombination on chromosome 4 in wild type; and (c) despite being normally achiasmate, chromosome 4 responds to recombination-defective meiotic mutants in the same way as do the other chromosomes.

GENETIC ANALYSIS OF SEX CHROMOSOMAL MEIOTIC MUTANTS IN DROSOPHILA MELANOGASTER

Genetics ◽  
1972 ◽  
Vol 71 (2) ◽  
pp. 255-286
Author(s):  
Bruce S Baker ◽  
Adelaide T C Carpenter
Keyword(s):  
X Chromosome ◽  
Meiotic Division ◽  
Sex Chromosome ◽  
Meiotic Drive ◽  
Chromosome 2 ◽  
Fourth Chromosome ◽  
X Chromosomes ◽  
Meiotic Mutants ◽  
Male Specific ◽  
Chromosome Nondisjunction

ABSTRACT A total of 209 ethyl methanesulfonate-treated X chromosomes were screened for meiotic mutants that either (1) increased sex or fourth chromosome nondisjunction at either meiotic division in males; (2) allowed recombination in such males; (3) increased nondisjunction of the X chromosome at either meiotic division in females; or (4) caused such females, when mated to males heterozygous for Segregation-Distorter (SD) and a sensitive homolog to alter the strength of meiotic drive in males.—Twenty male-specific meiotic mutants were found. Though the rates of nondisjunction differed, all twenty mutants were qualitatively similar in that (1) they alter the disjunction of the X chromosome from the Y chromosome; (2) among the recovered sex-chromosome exceptional progeny, there is a large excess of those derived from nullo-XY as compared to XY gametes; (3) there is a negative correlation between the frequency of sex-chromosome exceptional progeny and the frequency of males among the regular progeny. In their effects on meiosis these mutants are similar to In(1)sc4Lsc8R, which is deleted for the basal heterochromatin. These mutants, however, have normal phenotypes and viabilities when examined as X/0 males, and furthermore, a mapping of two of the mutants places them in the euchromatin of the X chromosome. It is suggested that these mutants are in genes whose products are involved in insuring the proper functioning of the basal pairing sites which are deleted in In(1)sc4Lsc8R, and in addition that there is a close connection, perhaps causal, between the disruption of normal X-Y pairing (and, therefore, disjunction) and the occurrence of meiotic drive in the male.—Eleven mutants were found which increased nondisjunction in females. These mutants were characterized as to (1) the division at which they acted; (2) their effect on recombination; (3) their dominance; (4) their effects on disjunction of all four chromosome pairs. Five female mutants caused a nonuniform decrease in recombination, being most pronounced in distal regions, and an increase in first division nondisjunction of all chromosome pairs. Their behavior is consistent with the hypothesis that these mutants are defective in a process which is a precondition for exchange. Two female mutants were allelic and caused a uniform reduction in recombination for all intervals (though to different extents for the two alleles) and an increase in first-division nondisjunction of all chromosomes. Limited recombination data suggest that these mutants do not alter coincidence, and thus, following the arguments of Sandler et al. (1968), are defective in exchange rather than a precondiiton for exchange. A single female mutant behaves in a manner that is consistent with it being a defect in a gene whose functioning is essential for distributive pairing. Three of the female meiotic mutants cause abnormal chromosome behavior at a number of times in meiosis. Thus, nondisjunction at both meiotic divisions is increased, recombinant chromosomes nondisjoin, and there is a polarized alteration in recombination.—The striking differences between the types of control of meiosis in the two sexes is discussed and attention is drawn to the possible similarities between (1) the disjunction functions of exchange and the process specified by the chromosome-specific male mutants; and (2) the prevention of functional aneuploid gamete formation by distributive disjunction and meiotic drive.

TEMPERATURE-SENSITIVE MUTATIONS IN DROSOPHILA MELANOGASTER: XX. LETHALITY DUE TO TRANSLOCATIONS

1974 ◽  
Vol 16 (3) ◽  
pp. 579-592 ◽  
Author(s):  
Thomas C. Kaufman ◽  
David T. Suzuki
Keyword(s):  
Drosophila Melanogaster ◽  
Temperature Sensitivity ◽  
Position Effect ◽  
Temperature Sensitive ◽  
Crossing Over ◽  
Lethal Mutations ◽  
New Type ◽  
Γ Ray ◽  
Developmental Analysis ◽  
Ts Mutations

In a group of 10 γ-ray-induced temperature-sensitive (ts) lethal mutations on the X chromosome of Drosophila melanogaster, three were found to inhibit crossing over on this element. Subsequent studies showed that these three ts lethal mutations are associated with X [Formula: see text] autosome translocations. Developmental analysis has revealed that the patterns of temperature-sensitivity and lethality are similar to those found in other ts mutations. One of the mutations (T(X;2)X9ts) is unique, however, in that only males exhibit temperature-sensitive lethality while homozygous females are unaffected by a change in temperature. It is proposed that these three mutations may be exhibiting some new type of "position effect".

scholarly journals MUTATIONS IN GENES ENCODING ESSENTIAL MITOTIC FUNCTIONS IN DROSOPHILA MELANOGASTER

Genetics ◽  
1985 ◽  
Vol 110 (4) ◽  
pp. 647-670
Author(s):  
David A Smith ◽  
Bruce S Baker ◽  
Maurizio Gatti
Keyword(s):  
Drosophila Melanogaster ◽  
Mitotic Chromosome ◽  
Chromosome Instability ◽  
Temperature Sensitive ◽  
Chromosome Behavior ◽  
Chromosome Transmission ◽  
Genes Encoding ◽  
Genetic Techniques ◽  
Elevated Frequency ◽  
Chromosome Integrity

ABSTRACT Temperature-sensitive mutations at 15 loci that affect the fidelity of mitotic chromosome behavior have been isolated in Drosophila melanogaster. These mitotic mutants were detected in a collection of 168 EMS-induced X-linked temperature-sensitive (ts) lethal and semilethal mutants. Our screen for mutations with mitotic effects was based upon the reasoning that under semirestrictive conditions such mutations could cause an elevated frequency of mitotic chromosome misbehavior and that such events would be detectable with somatic cell genetic techniques. Males hemizygous for each ts lethal and heterozygous for the recessive autosomal cell marker mwh were reared under semirestrictive conditions, and the wings of those individuals surviving to adulthood were examined for an increased frequency of mwh clones. Those mutations producing elevated levels of chromosome instability during growth of the wing imaginal disc were also examined for their effects on chromosome behavior in the cell lineages producing the abdominal cuticle. Fifteen mutations affect chromosome behavior in both wing and abdominal cells and thus identify loci generally required for the fidelity of mitotic chromosome transmission. Mapping and complementation tests show that these mutations represent 15 loci. One mutant is an allele of a locus (mus-101) previously identified by mutagensensitive mutants and a second mutant is an allele of the lethal locus zw10.—The 15 mutants were also examined cytologically for their effects on chromosomes in larval neuroblasts. Taken together, the results of our cytological and genetical studies show that these mutants identify loci with wild-type functions necessary for either (1) maintenance of chromosome integrity or (2) regular disjunction of chromosomes or (3) chromosome condensation. Thus, these mutations define a broad spectrum of genes required for the normal execution of the mitotic chromosome cycle.

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