Dependence on genie balance for synaptonemal complex formation in Drosophila melanogaster

Electron microscopic examination of gonads of Drosophila melanogaster with different genotypes, including a metafemale 3X;2A and an intersex XXY;3A, have revealed that the formation of synaptonemal complexes is controlled by the genie balance, i.e., the ratio of X chromosomes to autosomes. The Y chromosome is not involved in the genetic control of the formation of precursors of the central element of synaptonemal complexes in males, nor does it disturb their formation in [Formula: see text] females. Hyperploidy for sections 1 – 3A and 18A – 20 of the X chromosome does not lead to the appearance of synaptonemal complexes in males and does not interfere with their formation in females. Females hyperploid for extensive regions of the X chromosome (sections 1 – 11A, 11A – 20, and 8C – 20) are fertile and show apparently normal formation of synaptonemal complexes. Hyperploidy for sections 8C – 11A of the X results in a sharp decrease in the viability of females, in abnormal differentiation of ovary cells, and in the lack of synaptonemal complexes. These data suggest a possible important role for the sections 8C – 11A in the genic balance controlling the formation of synaptonemal complexes in D. melanogaster. The lack of synaptonemal complexes in hypoploid females may be the result of abnormal cell differentiation in gonads.Key words: Drosophila melanogaster, synaptonemal complex, sex chromosomes, genic balance.

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A TECHNIQUE FOR LIGHT AND ELECTRON MICROSCOPY OF THE SYNAPTONEMAL COMPLEX OF THE MOUSE OOCYTE

Canadian Journal of Genetics and Cytology ◽

10.1139/g82-071 ◽

1982 ◽

Vol 24 (6) ◽

pp. 675-680 ◽

Cited By ~ 8

Author(s):

Weng Kong Sung ◽

Georgiana Jagiello

Keyword(s):

Electron Microscopy ◽

Synaptonemal Complex ◽

Microscopic Examination ◽

Light And Electron Microscopy ◽

Electron Microscopic Examination ◽

Mouse Oocyte ◽

Electron Microscopic ◽

Synaptonemal Complexes

A method is described for obtaining synaptonemal complex preparations from mouse pachytene oocytes for light and electron microscopic examination. A karyotype based on the whole complement of synaptonemal complexes of a pachytene oocyte as visualized by electron microscopy is presented.

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SITE-SPECIFIC INSTABILITY IN DROSOPHILA MELANOGASTER: EVIDENCE FOR TRANSPOSITION OF DESTABILIZING ELEMENT

Genetics ◽

10.1093/genetics/101.3-4.461 ◽

1982 ◽

Vol 101 (3-4) ◽

pp. 461-476

Author(s):

Todd R Laverty ◽

J K Lim

Keyword(s):

Drosophila Melanogaster ◽

X Chromosome ◽

Lethal Mutation ◽

Chromosome Rearrangements ◽

Chromosome Break ◽

Secondary Mutation ◽

X Chromosomes ◽

Site Specific ◽

Normal Sequence ◽

Lethal Mutations

ABSTRACT In this study, we show that at least one lethal mutation at the 3F-4A region of the X chromosome can generate an array of chromosome rearrangements, all with one chromosome break in the 3F-4A region. The mutation at 3F-4A (secondary mutation) was detected in an X chromosome carrying a reverse mutation of an unstable lethal mutation, which was mapped in the 6F1-2 doublet (primary mutation). The primary lethal mutation at 6F1-2 had occurred in an unstable chromosome (Uc) described previously (Lim 1979). Prior to reversion, the 6F1-2 mutation had generated an array of chromosome rearrangements, all having one break in the 6F1-2 doublet (Lim 1979, 1980). In the X chromosomes carrying the 3F-4A secondary lethal mutation the 6F1-2 doublet was normal and stable, as was the 3F-4A region in the X chromosome carrying the primary lethal mutation. The disappearance of the instability having a set of genetic properties at one region (6F1-2) accompanied by its appearance elsewhere in the chromosome (3F-4A) implies that a transposition of the destabilizing element took place. The mutant at 3F-4A and other secondary mutants exhibited all but one (reinversion of an inversion to the normal sequence) of the eight properties of the primary lethal mutations. These observations support the view that a transposable destabilizing element is responsible for the hypermutability observed in the unstable chromosome and its derivaties.

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Hybrid dysgenesis-induced quantitative variation on the X chromosome of Drosophila melanogaster.

Genetics ◽

10.1093/genetics/124.3.627 ◽

1990 ◽

Vol 124 (3) ◽

pp. 627-636

Author(s):

C Q Lai ◽

T F Mackay

Keyword(s):

Drosophila Melanogaster ◽

X Chromosome ◽

Quantitative Traits ◽

Natural Populations ◽

Quantitative Variation ◽

Hybrid Dysgenesis ◽

X Chromosomes ◽

Bristle Number ◽

Seven Generations ◽

Polygenic Variation

Abstract To determine the ability of the P-M hybrid dysgenesis system of Drosophila melanogaster to generate mutations affecting quantitative traits, X chromosome lines were constructed in which replicates of isogenic M and P strain X chromosomes were exposed to a dysgenic cross, a nondysgenic cross, or a control cross, and recovered in common autosomal backgrounds. Mutational heritabilities of abdominal and sternopleural bristle score were in general exceptionally high-of the same magnitude as heritabilities of these traits in natural populations. P strain chromosomes were eight times more mutable than M strain chromosomes, and dysgenic crosses three times more effective than nondysgenic crosses in inducing polygenic variation. However, mutational heritabilities of the bristle traits were appreciable for P strain chromosomes passed through one nondysgenic cross, and for M strain chromosomes backcrossed for seven generations to inbred P strain females, a result consistent with previous observations on mutations affecting quantitative traits arising from nondysgenic crosses. The new variation resulting from one generation of mutagenesis was caused by a few lines with large effects on bristle score, and all mutations reduced bristle number.

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The synaptonemal complexes of Achlya recurva (Oomycetes): karyotype analysis and three-dimensional reconstruction of pachytene nuclei in antheridia and oogonia

Canadian Journal of Botany ◽

10.1139/b91-178 ◽

1991 ◽

Vol 69 (6) ◽

pp. 1384-1395 ◽

Cited By ~ 2

Author(s):

Hobart R. Williamson ◽

Pesach Ben Yitzchak

Keyword(s):

Synaptonemal Complex ◽

Organizer Region ◽

Nucleolar Organizer Region ◽

Nucleolus Organizer Region ◽

Three Dimensional ◽

Central Element ◽

Three Dimensional Reconstruction ◽

Synaptonemal Complexes ◽

Sequence Of Events ◽

Dimensional Reconstruction

Fifteen synaptonemal complexes, as determined by three-dimensional reconstruction of serial, ultrathin sections, were present within both antheridial and oogonial zygotene and pachytene nuclei of the oomyceteous fungus Achlya recurva, thus n = 15. The present study represents the first complete reconstruction of synaptonemal complexes in the genus Achlya. The occurrence of both zygonema and pachynema was simultaneous in antheridia and oogonia. Pachytene nuclei of antheridia and oogonia are small, 13 μm3 in volume, and the average length of the synaptonemal complexes ranged from 1.9 to 4.4 μm. Lateral elements at zygotene ranged from 1.2 to 4.7 μm. Both ends of each synaptonemal complex were attached randomly to the nuclear envelope, so a bouquet formation was not observed at pachytene. In A. recurva, the dimensions of the synaptonemal complex were as follows: overall width = 270 nm; the lateral elements = 75 nm each in width and the central region = 120 nm. There was no central element and associated transverse filaments, which may be associated with development of alternative reproductive strategies other than amphimixis, as in nematodes. Of the 15 synaptonemal complexes present, only the one carrying the nucleolus organizer region could be clearly identified from one nucleus to the next. The nucleolar organizer region was on the average 0.75 μm from the telomere in both zygotene and pachytene nuclei. There were an average of three recombination nodules in each nucleus. Synaptonemal complexes have been reported in over 80 different species of fungi and related protista. Karyotypic evolution in the oomycetes and fungi may be the result of poly-ploidization, followed by cytogenetic diversification involving aneuploidy and differing degrees of polyploidy. Such a sequence of events could explain the apparent polyphyletic formation of this group. Key words: karyotype, Oomycetes, pachytene, synaptonemal complexes, three-dimensional reconstruction.

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Spontaneous formation of compound X chromosomes in Drosophila melanogaster.

Genetics ◽

10.1093/genetics/119.1.95 ◽

1988 ◽

Vol 119 (1) ◽

pp. 95-103

Author(s):

R J Morrison ◽

J D Raymond ◽

J R Zunt ◽

J K Lim ◽

M J Simmons

Keyword(s):

Drosophila Melanogaster ◽

X Chromosome ◽

The Other ◽

X Chromosomes ◽

Multiple Factors ◽

Spontaneous Formation ◽

Chromosome Attachment ◽

Recombination Experiments ◽

Attachment Process

Abstract Males carrying different X chromosomes were tested for the ability to produce daughters with attached-X chromosomes. This ability is characteristic of males carrying an X chromosome derived from 59b-z, a multiply marked X chromosome, and is especially pronounced in males carrying the unstable 59b-z chromosomes Uc and Uc-lr. Recombination experiments with one of the Uc-lr chromosomes showed that the formation of compound chromosomes depends on two widely separated segments. One of these is proximal to the forked locus and is probably proximal to the carnation locus. This segment may contain the actual site of chromosome attachment. The other essential segment lies between the crossveinless and vermilion loci and may contain multiple factors that influence the attachment process.

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MEIOTIC BEHAVIOR OF COMPOUND AUTOSOMES IN FEMALES OF DROSOPHILA MELANOGASTER: INTERCHROMOSOMAL EFFECTS AND THE SOURCE OF SPONTANEOUS NONSEGREGATION

Genetics ◽

10.1093/genetics/96.2.455 ◽

1980 ◽

Vol 96 (2) ◽

pp. 455-470

Author(s):

Hideh Harger ◽

David G Holm

Keyword(s):

Drosophila Melanogaster ◽

X Chromosome ◽

Inverse Correlation ◽

Proximal Region ◽

Crossing Over ◽

X Chromosomes ◽

Repulsion Phase ◽

Base Level ◽

Exchange Processes ◽

Spontaneous Frequency

ABSTRACT In females of Drosophila melanogaster, compound autosomes enter the repulsion phase of meiosis uncommitted to a particular segregation pattern because their centromeres are not restricted to a bivalent pairing complex as a consequence of crossing over. Their distribution at anaphase, therefore, is determined by some meiotic property other than exchange pairing, a property that for many years has been associated with the concept of nonhomologous pairing. In the absence of heterologous rearrangements or a free Y chromosome, C(3L) and C(3R) are usually recovered in separate gametes, that is as products of meiotic segregation. Nevertheless, there is a regular, albeit infrequent, recovery of reciprocal meiotic products (the nonsegregational products) that are disomic and nullosomic for compound thirds. The frequency of these exceptions, which is normally between 0.5 and 5.0%, differs for the various strains examined, but remains constant for any given strain. Since previous studies have not uncovered a cause for this base level of nonsegregation, it has been referred to as the spontaneous frequency. In this study, crosses between males and females whose X chromosomes, as well as compound autosomes, are differentially marked reveal a highly significant positive correlation between the frequency of compound-autosome nonsegregation and the frequency of X-chromosome nondisjunction. However, an inverse correlation is found when the frequency of nondisjunction is related to the frequency of crossing over in the proximal region of the X chromosome. These findings have been examined with reference to the distributive pairing and the chromocentral models and interpreted as demonstrating (1) that nonsegregational meiotic events arise primarily as a result of nonhomologous interactions, (2) that forces responsible for the segregation of nonhomologous chromosomes are properties of the chromocentral region, and (3) that these forces come into expression after the exchange processes are complete.

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A cis-acting locus that promotes crossing over between X chromosomes in Caenorhabditis elegans.

Genetics ◽

10.1093/genetics/136.3.887 ◽

1994 ◽

Vol 136 (3) ◽

pp. 887-902 ◽

Cited By ~ 9

Author(s):

A M Villeneuve

Keyword(s):

Caenorhabditis Elegans ◽

X Chromosome ◽

Sharp Decrease ◽

Crossing Over ◽

Meiotic Pairing ◽

X Chromosomes ◽

Cis Acting ◽

Pairing Site ◽

High Level ◽

Pairing Center

Abstract This study reports the characterization of a cis-acting locus on the Caenorhabditis elegans X chromosome that is crucial for promoting normal levels of crossing over specifically between the X homologs and for ensuring their proper disjunction at meiosis I. The function of this locus is disrupted by the mutation me8, which maps to the extreme left end of the X chromosome within the region previously implicated by studies of X; A translocations and X duplications to contain a meiotic pairing site. Hermaphrodites homozygous for a deletion of the locus (Df/Df) or heterozygous for a deletion and the me8 mutation (me8/Df) exhibit extremely high level of X chromosome nondisjunction at the reductional division; this is correlated with a sharp decrease in crossing over between the X homologs as evidenced both by reductions in genetic map distances and by the presence of achiasmate chromosomes in cytological preparations of oocyte nuclei. Duplications of the wild-type region that are unlinked to the X chromosome cannot complement the recombination and disjunction defects in trans, indicating that this region must be present in cis to the X chromosome to ensure normal levels of crossing over and proper homolog disjunction. me8 homozygotes exhibit an altered distribution of crossovers along the X chromosome that suggests a defect in processivity along the X chromosome of an event that initiates at the chromosome end. Models are discussed in which the cis-acting locus deleted by the Dfs functions as a meiotic pairing center that recruits trans-acting factors onto the chromosomes to nucleate assembly of a crossover-competent complex between the X homologs. This pairing center might function in the process of homolog recognition, or in the initiation of homologous synapsis.

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MALE-STERILIZING INTERACTIONS BETWEEN DUPLICATIONS AND DEFICIENCIES FOR PROXIMAL X-CHROMOSOME MATERIAL IN DROSOPHILA MELANOGASTER

Genetics ◽

10.1093/genetics/99.1.49 ◽

1981 ◽

Vol 99 (1) ◽

pp. 49-64

Author(s):

Rezaur Rahman ◽

Dan L Lindsley

Keyword(s):

Drosophila Melanogaster ◽

X Chromosome ◽

Male Fertility ◽

Primary Spermatocyte ◽

Single Factor ◽

X Chromosomes ◽

Recessive Lethal ◽

Lethal Mutations ◽

Y Chromosomes ◽

Chromosome Material

ABSTRACT The genetic limits of sixty-four deficiencies in the vicinity of the euchromatic-heterochromatic junction of the X chromosome were mapped with respect to a number of proximal recessive lethal mutations. They were also tested for male fertility in combination with three Y chromosomes carrying different amounts of proximal X-chromosome-derived material (BSYy+, y+Ymal126 and y + Ymal +). All deficiencies that did not include the locus of bb and a few that did were male-fertile in all male-viable Df(1)/Dp(1;Y) combinations. Nineteen bb deficiencies fell into six different classes by virtue of their male-fertility phenotypes when combined with the duplicated Y chromosomes. The six categories of deficiencies are consistent with a formalism that invokes three factors or regions at the base of the X, one distal and two proximal to bb, which bind a substance critical for precocious inactivation of the X chromosome in the primary spermatocyte. Free duplications carrying these regions or factors compete for the substance in such a way that, in the presence of such duplications, proximally deficient X chromosomes are unable to command sufficient substance for proper control of X-chromosome gene activity preparatory to spermatogenesis. We conclude that there is no single factor at the base of the X that is required for the fertility of males whose genotype is otherwise normal.

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FITNESS EFFECTS OF EMS-INDUCED MUTATIONS ON THE X CHROMOSOME OF DROSOPHILA MELANOGASTER. II. HEMIZYGOUS FITNESS EFFECTS

Genetics ◽

10.1093/genetics/87.4.775 ◽

1977 ◽

Vol 87 (4) ◽

pp. 775-783

Author(s):

Joyce A Mitchell ◽

Michael J Simmons

Keyword(s):

Drosophila Melanogaster ◽

X Chromosome ◽

Induced Mutations ◽

Fitness Effect ◽

X Chromosomes ◽

Fitness Effects ◽

Induced Mutants ◽

Time Changes

ABSTRACT X chromosomes mutagenized with EMS were tested for their effects on the fitness of hemizygous carriers. The tests were carried out in populations in which treated and untreated X chromosomes segregated from matings between males and attached-X females; the populations were maintained for several generations, during which time changes in the frequencies of the treated and untreated chromosomes were observed. From the rates at which the frequencies changed, the fitness effects of the treated chromosomes were determined. It was found that flies hemizygous for a mutagenized chromosome were 1.7% less fit per mm EMS treatment than those hemizygous for an untreated chromosome. Since the same flies were only 0.5% per m m less viable than their untreated counterparts, the total fitness effect of an X chromosome carrying EMS-induced mutants is three to four times greater than its viability effect. By comparing the heterozygous effect of a mutagenized X chromosome on fitness with the corresponding hemizygous effect, the dominance value for the chromosome is estimated to be about 0.25.

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Heterochromatin, the synaptonemal complex and crossing over

Journal of Cell Science ◽

10.1242/jcs.71.1.159 ◽

1984 ◽

Vol 71 (1) ◽

pp. 159-176 ◽

Cited By ~ 1

Author(s):

S.M. Stack

Keyword(s):

Electron Microscopy ◽

Lycopersicon Esculentum ◽

Synaptonemal Complex ◽

Electron Microscopic Examination ◽

Differential Staining ◽

Crossing Over ◽

Mitotic Metaphase ◽

Plantago Ovata ◽

Electron Microscopic ◽

Metaphase Chromosomes

A combined light- and electron-microscopic examination of chromosomes from two angiospermous plants, Plantago ovata and Lycopersicon esculentum, and a mammal, Mus musculus, was performed. From this investigation three observations have been made that may be relevant to the observed lack of crossing over in heterochromatin. (1) Differential staining indicates that heterochromatin represents a smaller fraction of the length of pachytene chromosomes than it represents in the length of mitotic metaphase chromosomes. Since the synaptonemal complex (SC) runs throughout the length of these pachytene chromosomes, it is under-represented in heterochromatin. Considering the evidence for a rough correlation between the length of SC and the amount of crossing over, this could result in less crossing over in heterochromatin than expected on the basis of its length in mitotic metaphase chromosomes. (2) Electron microscopy indicates that, unlike the SC in euchromatin, the SC in heterochromatin is densely ensheathed in highly compact chromatin. If crossing over occurs in the SC or even in the surrounding chromatin, the compaction of the chromatin may prevent the penetration of enzymes needed in recombination. (3) Finally, a difference in the structure of SCs in euchromatin versus heterochromatin was observed that could be associated with the lack of crossing over in heterochromatin.

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