scholarly journals RECOMBINATION AND DNA REPLICATION IN THE DROSOPHILA MELANOGASTER OOCYTE

Genetics ◽  
1973 ◽  
Vol 73 (1) ◽  
pp. 87-108
Author(s):  
Rhoda F Grell
Keyword(s):  
Drosophila Melanogaster ◽  
Dna Replication ◽  
Present Method ◽  
Sensitive Period ◽  
Crossing Over ◽  
Drosophila Genome ◽  
Chromosome 2

ABSTRACT A method is described that permits the recovery of a well-synchronized population of oocytes. Utilizing this pupal system, the heat-responsive period for increasing crossing-over in the Drosophila genome has been defined for the Χ chromosome and a portion of chromosome 2. The response is initiated close to the time of oocyte formation (premeiotic interphase) and is terminated after ~36 hr. During the 36-hr period different regions show characteristic responses, which vary in degree, in duration, and in initiation and termination points, so as to generate the beginning of a thermal recombination map for the Drosophila genome. Centromere regions exhibit the greatest increases in crossing-over for their respective chromosomes but are distinctly asynchronous in time; interstitial regions respond the least. Correlated autoradiographic studies have localized DNA replication in the oocyte to a ~24-hr period, which also begins close to oocyte formation (premeiotic interphase); late labeling in restricted regions, undetectable with the present method, could extend the period, as could prolonged synthesis in the oocyte. The results demonstrate that DNA replication and the heat-sensitive period for enhancement of crossing-over are coincident processes over most and possibly all of their length.

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 Using the P{wHy} Hybrid Transposable Element to Disrupt Genes in Region 54D-55B in Drosophila melanogaster

Genetics ◽  
2002 ◽  
Vol 162 (1) ◽  
pp. 165-176 ◽  
Author(s):  
Stephanie E Mohr ◽  
William M Gelbart
Keyword(s):  
Drosophila Melanogaster ◽  
Transposable Element ◽  
Model Organism ◽  
Drosophila Genome ◽  
Chromosome 2 ◽  
Lethal Mutations ◽  
F Region ◽  
Nested Sets ◽  
Mutant Phenotypes ◽  
Improved Methods

Abstract Understanding the function of each gene in the genome of a model organism such as Drosophila melanogaster is an important goal. The development of improved methods for uncovering the mutant phenotypes of specific genes can accelerate achievement of this goal. The P{wHy} hybrid transposable element can be used to generate nested sets of precisely mapped deletions in a given region of the Drosophila genome. Here we use the P{wHy} method to generate overlapping, molecularly defined deletions from a set of three P{wHy} insertions in the 54E-F region of chromosome 2. Deletions that span a total of 0.5 Mb were identified and molecularly mapped precisely. Using overlapping deletions, the mutant phenotypes of nine previously uncharacterized genes in a 101-kb region were determined, including identification of new loci required for viability and female fertility. In addition, the deletions were used to molecularly map previously isolated lethal mutations. Thus, the P{wHy} method provides an efficient method for systematically determining the phenotypes of genes in a given region of the fly genome.

scholarly journals A COMPARISON OF HEAT AND INTERCHROMOSOMAL EFFECTS ON RECOMBINATION AND INTERFERENCE IN DROSOPHILA MELANOGASTER

Genetics ◽  
1978 ◽  
Vol 89 (1) ◽  
pp. 65-77
Author(s):  
R F Grell
Keyword(s):  
Drosophila Melanogaster ◽  
X Chromosome ◽  
Thermal Dissociation ◽  
Temporal Sequence ◽  
The Other ◽  
Centromeric Heterochromatin ◽  
Drosophila Genome ◽  
Chromosome 2 ◽  
Independent Control ◽  
Order Of Magnitude

ABSTRACT Heat and interchromosomal effects on recombination have been compared for 23 regions comprising the predominantly euchromatic portions of the five arms of the Drosophila genome. Patterns of response are strikingly similar, with both modifiers causing proximal and distal increases and minimal effects in the middle of the arms. Changes in interference for the same regions in the presence of the two modifiers reveal little similarity, except for the X chromosome. The question of independent control of interference and recombination, as well as alternatives for their temporal sequence, is discussed. Recombination response to the two modifiers in the centric heterochromatin of chromosoaime 2 is markedly different from that found in euchromatin. The interchromosomal effect is absent here, whereas heat induces an increase roughly an order of magnitude greater than that found in euchromatin and totally unlike the lack of response in the proximal heterochromatin of the X chromosome. It is proposed that the sequestering of DNA satellite I (thermal dissociation 9-20° lower than that of the other major satellites) in the centromeric heterochromatin of chromosome 2 (but not in X or 3) may account for the increase.

scholarly journals EXTRACHROMOSOMAL ELEMENT DELTA IN DROSOPHILA MELANOGASTER. IX. INDUCTION OF DELTA-RETAINING CHROMOSOME LINES BY MUTATION AND GENE MAPPING

Genetics ◽  
1973 ◽  
Vol 74 (3) ◽  
pp. 477-487
Author(s):  
Sumio Minamori ◽  
Kinue Sugimoto
Keyword(s):  
Drosophila Melanogaster ◽  
Crossing Over ◽  
Chromosomal Gene ◽  
Ethyl Methane Sulfonate ◽  
Methane Sulfonate ◽  
Multiple Alleles ◽  
Ethyl Methane ◽  
Extrachromosomal Element ◽  
Polygenic System ◽  
Killing Action

ABSTRACT [Delta b], symbolized as [δb], is retained by Sb chromosome lines and transmitted through the females to their progeny. Transmission through the males is not directly demonstrable (Minamori 1969a). [delta r], symbolized as [δr], is retained by Sr chromosome lines and transmitted biparentally (Minamori 1971). The multiplication of delta is suppressed at low temperature. All descendant lines derived from Sb-carrying or Sr-carrying flies in which the presence of delta cannot be demonstrated gradually accumulate their specific delta factors over many generations (Minamori 1969b, 1972). The delta factors and the sensitive chromosomes are inseparably associated. This observation led to the assumption that delta may be a copy of a chromosomal gene or a certain agent integrated into the chromosome (Minamori 1972). This assumption was examined in the present study by experiments designed to induce delta-retaining sensitive chromosomes, and to map the gene(s) responsible for delta-retention and/or for sensitivity to the killing action of delta factor. One sensitive chromosome which retained [δb] (Sb chromosome) was obtained in the presence of [δb] out of 2492 insensitive chromosomes which retained no delta; in addition one Sb chromosome was obtained in the presence of [δr] out of 2131 insensitives. The latter finding suggests that Sb might be induced by a mutation caused by [δb] or [δr], but not by integration of either delta into the chromosome. Four Sb chromosomes and one sensitive chromosome which retained [δr] (Sr chromosome) were obtained out of 1970 insensitives when males carrying the chromosome were fed an alkylating mutagen, ethyl methane sulfonate (EMS). The location of delta-retaining genes was examined by crossing-over experiments employing eight Sb and five Sr chromosomes. The genes on these chromosomes were found to be located in the same region or near one another. The gene for [δb], symbolized as Dab, and the gene for [δr], symbolized as Dar, are assumed to be multiple alleles of a locus at 2-24.9. The sensitivity of the chromosomes was modified appreciably by recombination; hence, the genes controlling this trait are assumed to be a polygenic system. The findings obtained in this study lead to the hypothesis that delta may be produced by a chromosomal gene (Da) and transmitted extrachromosomally.

scholarly journals ORIENTATION DISRUPTOR (ord): A RECOMBINATION-DEFECTIVE AND DISJUNCTION-DEFECTIVE MEIOTIC MUTANT IN DROSOPHILA MELANOGASTER

Genetics ◽  
1976 ◽  
Vol 84 (3) ◽  
pp. 545-572
Author(s):  
James M Mason
Keyword(s):  
Drosophila Melanogaster ◽  
Genetic Map ◽  
Crossing Over ◽  
Prophase I ◽  
Sister Chromatids

ABSTRACT The effects of a semidominant autosomal meiotic mutant, orientation disruptor (symbol: ord), located at 2-103.5 on the genetic map and in region 59B-D of the salivary map, have been examined genetically and cytologically. The results are as follows. (1) Crossing over in homozygous females is reduced to about seven percent of controls on all chromosomes, with the reduction greatest in distal regions. (2) Crossing over on different chromosomes is independent. (3) Reductional nondisjunction of any given chromosome is increased to about thirty percent of gametes from homozygous females. The probability of such nondisjunction is the same among exchange and nonexchange tetrads with the exception that a very proximal exchange tends to regularize segregation. (4) Equational nondisjunction of each chromosome is increased to about ten percent of gametes in homozygous females; this nondisjunction is independent of exchange. (5) The distributive pairing system is operative in homozygous females. (6) In homozygous males, reductional nondisjunction of each chromosome is increased to about ten percent, and equational nondisjunction to about twenty percent, of all gametes. (7) Cytologically, two distinct meiotic divisions occur in spermatocytes of homozygous males. The first division looks normal although occasional univalents are present at prophase I and a few lagging chromosomes are seen at anaphase I. However, sister chromatids of most chromosomes have precociously separated by metaphase II. Possible functions of the ord+ gene are considered.

scholarly journals A NOTE ON THE MATERNAL EFFECT MUTANTS DAUGHTERLESS AND ABNORMAL OOCYTE IN DROSOPHILA MELANOGASTER

Genetics ◽  
1973 ◽  
Vol 73 (1) ◽  
pp. 73-86
Author(s):  
Arthur P Mange ◽  
L Sandler
Keyword(s):  
Drosophila Melanogaster ◽  
Maternal Effect ◽  
Sex Chromosome ◽  
Chromosome 2 ◽  
Dominant Marker ◽  
Enhancing Effect ◽  
X Irradiation ◽  
The Right ◽  
Chromosome Breakpoint ◽  
Special Region

ABSTRACT Two deficiencies for, and a dominant enhancer of, the second chromosome maternal effect mutant, "daughterless" (da), were induced with X-irradiation. Their properties were studied with respect to both da and the linked maternal effect mutant, "abnormal oocyte" (abo), with the following conclusions. (1) The most probable map positions of da and abo are: J–½–da–2½–abo, where J is a dominant marker located at 41 on the standard map. (2) The da locus is in bands 31CD-F on the polytene chromosome map; abo is to the right of 32A. (3) Because homozygous da individuals survive while individuals carrying da and a deficiency for da are lethal, it is concluded that da is hypomorphic. (4) From a weak da-like maternal effect in heterozygous da females induced by an "Enhancer of da," we have confirmed a previous report that (a) the amount of sex chromosome heterochromatin contributed by the father can influence the severity of the da maternal effect, and (b) the sex chromosome heterochromatin which influences the da effect is different from that which influences the abo effect. (5) The possibility that da and abo are in a special region of chromosome 2 concerned with the regulation of sex chromosome heterochromatin is strengthened by the observation that the Enhancer of da appears to rescue abnormal eggs produced by homozygous abo mothers. (6) The Enhancer of da is a translocation between chromosomes 2 and 3 with the second chromosome breakpoint in the basal heterochromatin; because the enhancing effect maps in this region of chromosome 2, it is possible that autosomal, as well as sex chromosomal, heterochromatin interacts with da and abo.

scholarly journals Recombinogenic Effects of Suppressors of Position-Effect Variegation in Drosophila

Genetics ◽  
2002 ◽  
Vol 160 (2) ◽  
pp. 609-621
Author(s):  
Thomas Westphal ◽  
Gunter Reuter
Keyword(s):  
Chromatin Structure ◽  
Position Effect ◽  
Heterochromatic Region ◽  
Crossing Over ◽  
Position Effect Variegation ◽  
Chromosome 2 ◽  
Additive Effects ◽  
Suppressor Mutations ◽  
Effect Variegation ◽  
Meiotic Nondisjunction

Abstract Compact chromatin structure, induction of gene silencing in position-effect variegation (PEV), and crossing-over suppression are typical features of heterochromatin. To identify genes affecting crossing-over suppression by heterochromatin we tested PEV suppressor mutations for their effects on crossing over in pericentromeric regions of Drosophila autosomes. From the 46 mutations (28 loci) studied, 16 Su(var) mutations of the nine genes Su(var)2-1, Su(var)2-2, Su(var)2-5, Su(var)2-10, Su(var)2-14, Su(var) 2-15, Su(var)3-3, Su(var)3-7, and Su(var)3-9 significantly increase in heterozygotes or by additive effects in double and triple heterozygotes crossing over in the ri-pp region of chromosome 3. Su(var)2-201 and Su(var) 2-1401 display the strongest recombinogenic effects and were also shown to enhance recombination within the light-rolled heterochromatic region of chromosome 2. The dominant recombinogenic effects of Su(var) mutations are most pronounced in proximal euchromatin and are accompanied with significant reduction of meiotic nondisjunction. Our data suggest that crossing-over suppression by heterochromatin is controlled at chromatin structure as well as illustrate the possible effects of heterochromatin on total crossing-over frequencies in the genome.

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