Biomedical subjects

M M Green

Publications and source records attributed to M M Green.

At least 91 records · Page 5Linked to original sources

PubMed1976

Genetic controls of meiotic recombination and somatic DNA metabolism in Drosophila melanogaster.

Recombination-defective meiotic mutants and mutagen-sensitive mutants of D. melanogaster have been examined for their effects on meiotic chromosome behavior, sensitivity to killing by mutagens, somatic chromosome integrity, and DNA repair processes. Several loci have been identified that specify functions that are necessary for both meiotic recombination and DNA repair processes, whereas mutants at combination and DNA repair processes, whereas mutants at other loci appear to be defective in only one pathway of DNA processing.

Animals↗

PubMed1976

Evolution of experimental "mutator" populations of Drosophila melanogaster.

The theory of evolution predicts that the rate of adaptation of a population is a function of the amount of genetic variation present in the population. This has been experimentally demonstrated in Drosophila populations in which genetic variability was increased either by mass hybridization of two gene pools, or by X-irradiation.--Mutator genes increase the spontaneous mutation rates of their carriers. We have now studied the effects of a third-chromosome mutator gene, mt, on the rate of adaptation of laboratory populations. Initially, experimental and control populations had similar genetic constitutions except for the presence of absence of the mt gene. The populations were maintained for 20-25 generations by "serial transfer" under conditions of very intense selection.--The number of flies produced per unit time remained constant throughout the experiment in the experimental as well as in the control populations. However, in the mutator-carring populations the average longevity of the flies (and consequently the average population size) gradually decreased. Under the experimental conditions natural selection is unable to counteract completely the increased input of deleterious mutations due to the mt gene.

Animals↗

PubMed1976

Isolation and characterization of X-linked mutants of Drosophila melanogaster which are sensitive to mutagens.

Thirteen X-linked mutants have been isolated in Drosophila melanogaster which render male and homozygous female larvae sensitive to the mutagen methyl methanesulfonate. Their characterization and preliminary assignment to functional groups is described. Four of these mutants are alleles of mei-41 (Baker and Carpenter 1972). Like previously isolated alleles of this locus, these mutants reduce fertility and increase loss and nondisjunction of the X-chromosome in homozygous females. The remaining mutants have been tentatively assigned to six functional groups (two mutants to the mus(1)101 locus, two to mus(1)102 , two to mus(1)103, and one each to mus(1)104, mus(1)105 , and mus(1)106). Several of the complementation groups can be distinguished on the basis of nondisjunction and cross sensitivity to mutagens. Females homozygous for the mei-41, mus(1)101 and mus(1)102 mutants exhibit elevated levels of nondisjunction. Mutants belonging to complementation groups mei-41, mus(1)101, and mus(1)104 are sensitive to nitrogen mustard (HN2) in addition to their MMS sensitivity. Among these mutants there is currently a direct correlation between sensitivity to HN2, sensitivity to 2-acetylaminofluorene and a deficiency in post-replication repair ( Boyd and Setlow 1976). Only the mei-41 mutants are hypersensitive to UV radiation, although several of the mutants exhibit sensitivity to gamma-rays. Semidominance is observed in female larvae of the mei-41, mus(1)104, and mus(1)103 mutants after exposure to high concentrations of MMS. The properties of the mutants generally conform to a pattern which has been established for related mutants in yeast. Additional properties of these mutants are summarized in Table 9.

Alleles↗

PubMed1975

Conversion as a possible mechanism of high coincidence values in the centromere region of Drosophila.

Crossing over has been studied with mutants which flank the centromere of chromosome 3 in Drosophila melanogaster. Coefficients of coincidence greater than one were obtained. Putative double crossovers were recovered for genetic intervals whose genetic length is less than one centimorgan. It is suggested that gene conversion rather than conventional double crossing over accounts for the negative interference observed.

Animals↗

PubMed1975

Genetic instability in Drosophila melanogaster: Mutable miniature (mu).

A new mutable gene, mutable miniature wing (mu), is described. This mutable gene mutates spontaneously at an inordinate rate both germinally and somatically. Two classes of reversions of mu have been found in approximately equal frequency: those to an allele with an intermediate phenotype (mi) and those to a subliminal allele (ms) equivalent to wild type in phenotype. Reversions appear to be mutationally stable. The chronology of genetic events leading to the discovery of mu implicates, but does not prove, the insertion of a "foreign" DNA segment as the basis of mutability.

Alleles↗

PubMed1974