Search PubMed⌕ Search

Biomedical subjects

M G Kidwell

Publications and source records attributed to M G Kidwell.

14 recordsLinked to original sources
PubMed1992

Horizontal transfer of P elements and other short inverted repeat transposons.

Evidence for horizontal transfer of the P family of transposable elements in the genus Drosophila is reviewed and evaluated, along with observations consistent with the recent invasion of Drosophila melanogaster by these elements. Some other examples of horizontal transfer involving other groups of transposable elements having short inverted terminal repeats are also briefly described. The sequential mechanistic steps likely to be involved in a horizontal transfer event are explored, including the requirement for suitable interspecific vectors or carriers. Finally, the frequency and significance of horizontal transfer of transposable elements are briefly discussed within an evolutionary framework.

Animals↗
PubMed1992

Distribution of Drosophila melanogaster transposable element sequences in species of the obscura group.

Fifteen species belonging to the obscura group of the genus Drosophila were screened for sequences homologous to Drosophila melanogaster transposable elements (TEs) as an initial step in the examination of the possible occurrence of TEs at chromosomal inversion breakpoints. Blots of genomic DNAs from species of the obscura group were hybridized at three different stringencies with 14 probes representing the major families of TEs described in D. melanogaster. The probe DNAs included copia, gypsy, 412, 297, mdg1, mdg3, 3S18, F, G, I, jockey, P, hobo, and FB3. D. melanogaster TEs were not well represented in the species of the obscura group analyzed. The TEs that were observed generally exhibited heterogeneous distributions, with the exception of F, gypsy and 412 which were ubiquitous, and 297, G, Sancho 2, hobo and FB which were not detected.

Animals↗
PubMed1992

Horizontal transfer.

Eukaryotic transposable elements provide some of the best documented examples of the occasional horizontal transfer of DNA sequences between both closely and distantly related species. Although the mechanisms involved in such a transfer remain a puzzle, new ideas are beginning to emerge. The rapidly expanding number of reports of transposable elements that may have been transferred horizontally raises questions both about whether these elements are more prone to this mode of transfer than non-mobile genes, and about the possible evolutionary significance if such a difference is real.

Animals↗
PubMed1991

Possible horizontal transfer of Drosophila genes by the mite Proctolaelaps regalis.

There is strong inferential evidence for recent horizontal gene transfer of the P (mobile) element to Drosophila melanogaster from a species of the Drosophila willistoni group. One potential vector of this transfer is a semiparasitic mite, Proctolaelaps regalis DeLeon, whose morphology, behavior, and co-occurrence with Drosophila are consistent with the properties necessary for such a vector. Southern blot hybridization, polymerase chain reaction (PCR) amplification, and DNA sequencing showed that samples of P. regalis associated with a P strain of D. melanogaster carried P element sequences. Similarly, Drosophila ribosomal DNA sequences were identified in P. regalis samples that had been associated with Drosophila cultures. These results have potentially important evolutionary implications, not only for understanding the mechanisms by which genes may be transferred between reproductively isolated species, but also for improved detection of some host-parasite and predator-prey relationships.

Animals↗
PubMed1990

Evidence for horizontal transmission of the P transposable element between Drosophila species.

Several studies have suggested that P elements have rapidly spread through natural populations of Drosophila melanogaster within the last four decades. This observation, together with the observation that P elements are absent in the other species of the melanogaster subgroup, has lead to the suggestion that P elements may have entered the D. melanogaster genome by horizontal transmission from some more distantly related species. In an effort to identify the potential donor in the horizontal transfer event, we have undertaken an extensive survey of the genus Drosophila using Southern blot analysis. The results showed that P-homologous sequences are essentially confined to the subgenus Sophophora. The strongest P hybridization occurs in species from the closely related willistoni group. A wild-derived strain of D. willistoni was subsequently selected for a more comprehensive molecular examination. As part of the analysis, a complete P element was cloned and sequenced from this line. Its nucleotide sequence was found to be identical to the D. melanogaster canonical P, with the exception of a single base substitution at position 32. When the cloned element was injected into D. melanogaster embryos, it was able to both promote transposition of a coinjected marked transposon and induce singed-weak mutability, thus demonstrating its ability to function as an autonomous element. The results of this study suggest that D. willistoni may have served as the donor species in the horizontal transfer of P elements to D. melanogaster.

Animals↗
PubMed1976

Dynamics of correlated genetic systems. I. Selection in the region of the Glued locus of Drosophila melanogaster.

The dynamical behavior of chromosomal segments undergoing strong selection was investigated in four replicate populations of Drosophila melanogaster. This was accomplished by following the joint behavior of allozyme markers at the loci phosphoglucomutase and esterase C, adjacent to the recessive lethal locus Glued, during and following the course of selection against Glued. The results show strong selection at other loci in the region of the marked segment. Examination of the joint dynamic of the two markers indicates that there must be more than one, and probably several, selected loci in the region under observation, with large epistatic effects. The mode of selection on the segment often results in excess heterozygosity at the markers, but does not appear to be constant in time. It is concluded that the density of selective effects in the region under study is substantial.

Alleles↗
PubMed1976

Selection for male recombination in Drosophila melanogaster.

Two-way selection for male recombination over seven intervals of the third chromosome in Drosophila melanogaster was practiced for nine generations followed by relaxed selection for five generations. Significant responses in both directions were observed but these mainly occurred in early generations in the low line and in later generations in the high line. Divergence of male recombination frequencies between the two selection lines was not restricted to any specific region but occurred in every measured interval of the chromosome. However, right-arm intervals showed a more pronounced response than either left-arm intervals or the centromeric region. Correlated responses in sterility and distortion of transmission ratios occurred as a result of selection for male recombination. Cluster distributions of male recombinants suggested a mixture of meiotic and late gonial events but relative map distances more closely resembled those of the salivary chromosome than standard meiotic or mitotic distances. Patterns of male recombination over time in both second and third chromosomes strongly suggested a major effect associated with the presence of third chromosomes from the Harwich strain. Evidence was also found for modifiers with relatively small effects located in other regions of the genome. The overall results are interpreted in terms of a two-component model of hybrid dysgenesis.

Animals↗
PubMedDate not supplied

Spontaneous male recombination and mutation in isogenic-derived chromosomes of Drosophila melanogaster.

Spontaneous male recombination and visible mutations were observed in second and third chromosomes derived from an isogenic line, ID, previously found to exhibit a high recessive lethal mutation rate. All three types of events tend to occur very early in spermatogenesis resulting in large clusters of identical recombinant or mutant progeny from a single male. Mutations and male recombination exchange points tend to be located more frequently in the right arm than in the left in both second and third chromosomes but for a trivial reason in the case of chromosome 2. No significant differences in male or female recombination were found between the progeny of reciprocal crosses. Male recombination in chromosome 2, like recessive lethal mutation, is independent of the presence of ID third chromosomes in the same genome. Both quantitative and qualitative differences in male recombination were found when ID chromosomes were compared with others extracted from natural populations.

Animals↗
PubMedDate not supplied

Variation of the recombination fraction in Drosophila melanogaster females.

The distribution of the recombination fraction between two distal, autosomal loci, plexus and orange, was investigated in reciprocal crosses between the marker stock and each of two wild-type strains, Harwich and Ottawa. The dysgenic cross between Harwich males and marker females exhibited high sterility, low fecundity, and a non-normal distribution of the recombination fraction. Neither the distribution of the reciprocal Harwich cross nor those of the two Ottawa crosses deviated from normal. In general, the results support the view that the recombination fraction is a variable.

Animals↗
PubMedDate not supplied

Dynamics of natural selection on a lethal fourth chromosome of Drosophila. Twelve-generation study of experimental populations of D. melanogaster.

The dynamics of natural selection on a lethal fourth chromosome of Drosophila melanogaster was studied in replicated half-pint bottle and cage populations over 12 generations. Population numbers fluctuated widely in all populations, but there was no association between fluctuation in numbers and change in lethal frequency. In the bottle populations the lethal heterozygote frequency decreased to a low of 0.04 to 0.05 and then increased to 0.18 to 0.30, suggesting that the selection coefficients were not constant. In the cage populations heterozygote frequency decreased to about 0.35 to 0.40. In the cage populations the data suggest that the lethal chromosome is overdominant for both viability and fertility selection.

Animals↗