scholarly journals The distribution of transposable elements within and between chromosomes in a population of Drosophila melanogaster. II. Inferences on the nature of selection against elements

1992 ◽  
Vol 60 (2) ◽  
pp. 115-130 ◽  
Author(s):  
Brian Charlesworth ◽  
Angela Lapid ◽  
Darlene Canada
Keyword(s):  
Drosophila Melanogaster ◽  
Transposable Elements ◽  
Polytene Chromosomes ◽  
Element Abundance ◽  
General Tendency ◽  
Fourth Chromosome ◽  
Considerable Heterogeneity ◽  
Fitness Consequences ◽  
Random Expectation

SummaryData were collected on the distribution of nine families of transposable elements among a sample of autosomes isolated from a natural population of Drosophila melanogaster, by means of in situ hybridization of biotinylated probes to polytene chromosomes. There is no general tendency for elements to accumulate at the tips of chromosomes. Elements tend to be present in excess of random expectation in the euchromatin proximal to the centromeres of the major autosomes, and on chromosome four. There is considerable heterogeneity between different families in the extent of this excess. The overall abundance of element families is inversely related to the extent to which they accumulate proximally. The level of proximal accumulation for the major autosomes is similar to that on the fourth chromosome, but less than that for the X chromosome. There is an overall deficiency of elements in the mid-section of the X compared with the mid-sections of the major autosomes, with considerable heterogeneity between families. The magnitude of this deficiency is positively related to the extent to which elements accumulate proximally. No such deficiency is seen if the proximal regions of the X and autosomes are compared. There is a small and non-significant excess of elements in third chromosomes carrying inversions. There is some between-year heterogeneity in element abundance. The implications of these findings are discussed, and it is concluded that they generally support the hypothesis that transposable element abundance is regulated primarily by the deleterious fitness consequences of meiotic ectopic exchange between elements. If this is the case, such exchange must be very infrequent in the proximal euchromatin, and the elements detected in population surveys of this kind must be inserted into sites where they have negligible mutational effects on fitness.

scholarly journals Rates of movement and distribution of transposable elements in Drosophila melanogaster: in situ hybridization vs Southern blotting data

2001 ◽  
Vol 78 (2) ◽  
pp. 121-136 ◽  
Author(s):  
XULIO MASIDE ◽  
CAROLINA BARTOLOMÉ ◽  
STAVROULA ASSIMACOPOULOS ◽  
BRIAN CHARLESWORTH
Keyword(s):  
Drosophila Melanogaster ◽  
Transposable Elements ◽  
Southern Blotting ◽  
Polytene Chromosomes ◽  
Element Abundance ◽  
Data Sets ◽  
Copy Numbers ◽  
Blotting Technique ◽  
Controlling Element

Genomic copy numbers and the rates of movement of nine families of transposable elements (TEs) of Drosophila melanogaster were estimated in two sets of mutation accumulation lines: Beltsville and Madrid. Southern blotting was used to screen a large number of samples from both genetic backgrounds for TEs. The Madrid lines were also screened by in situ hybridization of TEs to polytene chromosomes, in order to obtain more detailed information about the behaviour of TEs in the euchromatin. Southern blotting data provided evidence of insertions and excision events in both genetic backgrounds, occurring at rates of approximately 10−5 and 10−6 per element copy per generation, respectively. In contrast, in situ data from the Madrid background presented a completely different picture, with no evidence for excisions, and a significantly higher rate of transposition (1·01×10−4). Direct comparison of the two data sets suggests that the Southern blotting technique had serious deficiencies: (i) it underestimated element abundance; (ii) it revealed less than 30% of the new insertions detected by in situ hybridization; and (iii) changes in the size of restriction fragments from any source were spuriously identified as simultaneous insertion–excision events. Our in situ data are consistent with previous studies, and suggest that selection is the main force controlling element spread by transposition.

scholarly journals The distribution of transposable elements within and between chromosomes in a population of Drosophila melanogaster. I. Element frequencies and distribution

1992 ◽  
Vol 60 (2) ◽  
pp. 103-114 ◽  
Author(s):  
Brian Charlesworth ◽  
Angela Lapid ◽  
Darlene Canada
Keyword(s):  
Population Dynamics ◽  
Drosophila Melanogaster ◽  
Linkage Disequilibrium ◽  
Transposable Elements ◽  
Copy Number ◽  
Polytene Chromosomes ◽  
Chromosome Band ◽  
High Frequencies ◽  
Copy Numbers

SummaryData were collected on the distribution of nine families of transposable elements among second and third chromosomes isolated from a natural population of Drosophila melanogaster, by means of in situ hybridization of element probes to polytene chromosomes. It was found that the copy numbers per chromosome in the distal sections of the chromosome arms followed a Poisson distribution. Elements appeared to be distributed randomly along the distal sections of the chromosome arms. There was no evidence for linkage disequilibrium in the distal sections of the chromosomes, but some significant disequilibrium was detected in proximal regions. There were many significant correlations between different element families with respect to the identity of the sites that were occupied in the sample. There were also significant correlations between families with respect to sites at which elements achieved relatively high frequencies. Element frequencies per chromosome band were generally low in the distal sections, but were higher proximally. These results are discussed in the light of models of the population dynamics of transposable elements. It is concluded that they provide strong evidence for the operation of a force or forces opposing transpositional increase in copy number. The data suggest that the rate of transposition perelement per generation is of the order of 10−4, for the elements included in this study.

scholarly journals Rates of movement of transposable elements on the second chromosome of Drosophila melanogaster

2000 ◽  
Vol 75 (3) ◽  
pp. 275-284 ◽  
Author(s):  
XULIO MASIDE ◽  
STAVROULA ASSIMACOPOULOS ◽  
BRIAN CHARLESWORTH
Keyword(s):  
Drosophila Melanogaster ◽  
Transposable Elements ◽  
Polytene Chromosomes ◽  
Mutation Accumulation ◽  
Long Terminal Repeats ◽  
Significant Difference ◽  
Transposable Element Copy ◽  
Excision Rate

The rates of movement of 11 families of transposable elements of Drosophila melanogaster were studied by means of in situ hybridization of probes to polytene chromosomes of larvae from a long-term mutation accumulation experiment. Replicate mutation-accumulation lines carrying second chromosomes derived from a single common ancestral chromosome were maintained by backcrosses of single males heterozygous for a balancer chromosome and a wild-type chromosome, and were scored after 116 generations. Twenty-seven transpositions and 1 excision were detected using homozygous viable and fertile second chromosomes, for a total of 235056 potential sources of transposition events and a potential 252880 excision events. The overall transposition rate per element per generation was 1·15×10−4 and the excision rate was 3·95×10−6. The single excision (of a roo element) was due to recombination between the element's long terminal repeats. A survey of the five most active elements among nine homozygous lethal lines revealed no significant difference in the estimates of transposition and excision rates from those from viable lines. The excess of transposition over excision events is in agreement with the results of other in situ hybridization experiments, and supports the conclusion that replicative increase in transposable element copy number is opposed by selection. These conclusions are compared with those from other studies, and with the conclusions from population surveys of element frequencies.

scholarly journals A study of ten families of transposable elements on X chromosomes from a population of Drosophila melanogaster

1989 ◽  
Vol 54 (2) ◽  
pp. 113-125 ◽  
Author(s):  
Brian Charlesworth ◽  
Angela Lapid
Keyword(s):  
Drosophila Melanogaster ◽  
Transposable Elements ◽  
Copy Number ◽  
Distal Part ◽  
Polytene Chromosomes ◽  
Chromosome Band ◽  
X Chromosomes ◽  
High Frequencies ◽  
Chromosome Element

SummaryData were collected on the distribution of ten families of transposable elements among fourteen X chromosomes isolated from a natural population of Drosophila melanogaster, by means of in situ hybridization to polytene chromosomes. It was found that, with the exception of roo, the copy number per chromosome followed a Poisson distribution. There was no evidence for linkage disequilibrium, either within or between families. Some pairs of families of elements were correlated with respect to the identity of the sites that were occupied in the sample, although there was no evidence for a correlation with respect to the sites at which elements attained relatively high frequencies. Elements appeared to be distributed randomly along the distal part of the X chromosome. There was, however, a strong tendency for elements to accumulate at the base of the chromosome. Element frequencies per chromosome band were generally low, except at the base of the chromosome where bands in subdivisions 19E and 20A sometimes had high frequencies of occupation. These results are discussed in the light of models of the population dynamics of transposable elements. It is concluded that they provide strong evidence for the operation of a force or forces opposing transpositional increase in copy number. The accumulation of elements at the base of the chromosome is consistent with the idea that unequal exchange between elements at non-homologous sites is such a force, although other possibilities cannot be excluded at present. The data suggest that the rate of transposition per element per generation is of the order of 10−4, for the elements included in this study.

scholarly journals The distribution of transposable elements within and between chromosomes in a population of Drosophila melanogaster. III. Element abundances in heterochromatin

1994 ◽  
Vol 64 (3) ◽  
pp. 183-197 ◽  
Author(s):  
Brian Charlesworth ◽  
Philippe Jarne ◽  
Stavroula Assimacopoulos
Keyword(s):  
Drosophila Melanogaster ◽  
Transposable Elements ◽  
Natural Population ◽  
Polytene Chromosomes ◽  
Control Element ◽  
Element Abundances ◽  
Evolutionary Forces ◽  
Isogenic Lines ◽  
Copy Numbers

SummaryThe total genomic copy numbers of ten families of transposable elements of Drosophila melanogaster in a set of ten isogenic lines derived from a natural population were estimated by slot-blotting. The numbers of euchromatic copies of members of each family were determined for each line by in situ hybridization of element probes to polytene chromosomes. Heterochromatic numbers were estimated by subtraction of the euchromatic counts from the total numbers. There was considerable variation between element families and lines in heterochromatic abundances, and the variance between lines for many elements was much greater for the heterochromatin than for the euchromatin. The data are consistent with the view that much of the β-heterochromatin consists of sequences derived from transposable elements. They are also consistent with the hypothesis that similar evolutionary forces control element abundances in both the euchromatin and heterochromatin, although amplification of inert sequences derived from transposable elements may be in part responsible for their accumulation in heterochromatin.

scholarly journals Chromosomal Distribution of Transposable Elements in Drosophila melanogaster Test of the Ectopic Recombination Model for Maintenance of Insertion Site Number

Genetics ◽  
1996 ◽  
Vol 144 (1) ◽  
pp. 197-204
Author(s):  
Christine Hoogland ◽  
Christian Biémont
Keyword(s):  
Drosophila Melanogaster ◽  
Transposable Elements ◽  
Dna Content ◽  
Recombination Rate ◽  
Alternative Hypothesis ◽  
Insertion Site ◽  
Polytene Chromosomes ◽  
Negative Relationship ◽  
Site Occupancy ◽  
Site Number

Abstract Data of insertion site localization and site occupancy frequency of P, hobo, I, copia, mdg1, mdg3, 412, 297, and roo transposable elements (TEs) on the polytene chromosomes of Drosophila melanogaster were extracted from the literature. We show that TE insertion site number per chromosomal division was significantly correlated with the amount of DNA. The insertion site number weighted by DNA content was not correlated with recombination rate for all TEs except hobo, for which a positive correlation was detected. No global tendency emerged in the relationship between TE site occupancy frequency, weighted by DNA content, and recombination rate; a strong negative correlation was, however, found for the 3L arm. A possible dominant deleterious effect of chromosomal rearrangements due to recombination between TE insertions is thus not the main factor explaining the dynamics of TEs, since this hypothesis implies a negative relationship between recombination rate and both TE insertion site number and site occupancy frequency. The alternative hypothesis of selection against deleterious effects of insertional mutations is discussed.

Quantitative in situ hybridization of ribosomal RNA species to polytene chromosomes of Drosophila melanogaster

1977 ◽  
Vol 115 (3) ◽  
pp. 539-563 ◽  
Author(s):  
Paul Szabo ◽  
Robert Elder ◽  
Dale M. Steffensen ◽  
Olke C. Uhlenbeck
Keyword(s):  
Drosophila Melanogaster ◽  
In Situ Hybridization ◽  
Ribosomal Rna ◽  
Polytene Chromosomes

Sequences isolated from a Drosophila early-ecdysone puff are expressed in rat liver

1984 ◽  
Vol 4 (5) ◽  
pp. 387-396 ◽  
Author(s):  
Carmen Arribas ◽  
Marta Izquierdo
Keyword(s):  
Drosophila Melanogaster ◽  
Rat Liver ◽  
Recombinant Dna ◽  
Polytene Chromosomes ◽  
Mammary Glands ◽  
Nucleic Acid Hybridization ◽  
Adult Rat ◽  
Dna And Rna ◽  
Polyadenylated Rna

We have studied the presence of a cloned fragment of DNA from Drosophila melanogaster in other organisms by means of nucleic acid hybridization analysis. The isolated region is localized in polytene chromosomes at the 63F subdivision. This region includes a puff that responds within minutes to ecdysone stimulation. We have found that 63F DNA from D. melanogaster hybridizes ‘in situ’ to both DNA and RNA from D. simulans, D. teissieri, and D. hydei. In all these species the isolated DNA remains associated with one early-ecdysone stimulated puff. The isolated Drosophila recombinant DNA is also complementary to polyadenylated RNA from foetal and adult rat liver but fails to hybridize to the nonpolyadenylated RNA classes from both sources and to polyadenylated RNA from rat mammary glands.

scholarly journals The fitness consequences of P element insertion in Drosophila melanogaster

1988 ◽  
Vol 52 (1) ◽  
pp. 17-26 ◽  
Author(s):  
Walter F. Eanes ◽  
Cedric Wesley ◽  
Jody Hey ◽  
David Houle ◽  
James W. Ajioka
Keyword(s):  
Drosophila Melanogaster ◽  
Relative Number ◽  
African Population ◽  
P Element ◽  
Insertion Event ◽  
Element Insertion ◽  
Lethal Mutations ◽  
Fitness Consequences ◽  
Per Se

SummaryIn this study we estimate the frequency at which P-element insertion events, as identified by in situ hybridization, generate lethal and mild viability mutations. The frequency of lethal mutations generated per insertion event was 0·004. Viability dropped an average of 1% per insertion event. Our results indicate that it is deletions and rearrangements resulting from the mobilization of P elements already in place and not the insertions per se that cause the drastic effects on viability and fitness observed in most studies of P–M dysgenesis-derived mutations. Elements of five other families (I, copia, 412, B104, and gypsy) were not mobilized in these crosses. Finally, we contrast the density of P elements on the X chromosome with the density on the four autosomal arms in a collection of thirty genomes from an African population. The relative number of P elements on the X chromosome is too high to be explained by either a hemizygous selection or a neutrality model. The possible reasons for the failure to detect selection are discussed.

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