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A cytoplasmically transmitted, diet-dependent difference in response to the teratogenic effects of 6-aminonicotinamide.

The frequency of congenital cleft palate produced by maternal treatment with 6-aminonicotinamide during pregnancy is lower in the C57BL/6J than in the A/J inbred mouse strain. In the C57BL/6J strain the frequency is lower when the mothers are maintained on Purina Lab Chow than when they are on Breeder Chow. A/J females do not show this effect of diet. There is a matroclinous reciprocal cross difference in frequency of induced cleft palate which persists in the back-cross when the F(1) mothers are maintained on Lab Chow but not on Breeder Chow.

Abnormalities, Drug-Induced↗

Cytoplasmic DNA from petite colonies of Saccharomyces cerevisiae: a hypothesis on the nature of the mutation.

The density of the cytoplasmic DNA of two strains of "petite" mutants of yeast, obtained by treatment with acriflavin and with ultraviolet light, was examined in cesium chloride density-gradient centrifugation and in all cases appeared to be less than that of the wild type. A cytoplasmic respiratory-deficient strain, treated with additional acriflavin, can show a further shift of the position of the satellite band, always in the direction of reduction of density. Also, from the p(+) x p(-) cross, p(-) strains can be recovered in which the density of the satellite DNA is different from the density of the parent p(-) strain. This finding suggests the existence of recombination in cytoplasmic DNA moleciules.

Acridines↗

Novel screening procedure for recombinant plasmids.

Lysed bacterial colonies containing potential recombinant plasmids were mixed with molten agar and sealed into slots of an agarose gel. After electrophoresis overnight, the gel was stained with ethidium bromide, which clearly reveals recombinant plasmids. Xenopus laevis ribosomal DNA and histone DNA of Psammechinus miliaris were ligated into pCRI plasmids and screened by this method.

Animals↗

Plasmid detection and sizing in single colony lysates.

A simple and contained procedure for the rapid assay of the presence and size of plasmids similar to Col El is described. Bacteria are picked from an agar plate with a toothpick, lysed with dodecyl sulfate and heat, and placed directly on an agarose gel for electrophoresis.

Colicins↗

Gene cloning and containment properties of plasmid Col E1 and its derivatives.

Colicinogenic plasmid E1 (Col E1) and Col E1 derivatives offer advantages as plasmid cloning vehicles with regard to both utility and biological containment. The Col E1 derivative pCR1 does not alter those essential characteristics of the enfeebled Escherichia coli strain x1776 that make this strain particularly useful as a host-vehicle system for recombinant DNA research.

Bile Acids and Salts↗

Increase in conjugational transmission frequency of nonconjugative plasmids.

Addition of Eco RI fragment 6 of the Escherichia coli sex factor F to pSC101 increases the frequency of its transmission by RI-19 and ColVB. Transmission frequencies of pSC101 and two pSC101 chimeras are also increased after the putative transposition of drug resistance element Tn3 from RI-19. These increases may result from addition of an origin of conjugatinal transfer to the plasmids.

Colicins↗

Rat insulin genes: construction of plasmids containing the coding sequences.

Recombinant bacterial plasmids have been constructed that contain complementary DNA prepared from rat islets of Langerhans messenger RNA. Three plasmids contain cloned sequences representing the complete coding region of rat proinsulin I, part of the preproinsulin I prepeptide, and the untranslated 3' terminal region of the mRNA. A fourth plasmid contains sequences derived from the A chain region of rat preproinsulin II.

Animals↗

Stable amplified DNA in drug-resistant Leishmania exists as extrachromosomal circles.

The relative stability of amplified DNA in drug-resistant Leishmania major was previously reported to be dependent on location, that is, unstable amplified DNA was extrachromosomal and stable amplified DNA was chromosomal. Leishmanial chromosomes have now been directly examined by means of orthogonal-field-alternation gel electrophoresis (OFAGE). The amplified DNA's in three resistant cell lines displayed unusual migration and were clearly extrachromosomal, regardless of whether the amplified DNA's were stable or unstable. Thus, contrary to conclusions from earlier studies of drug resistance in cultured animal cells, stable amplified DNA in Leishmania can be extrachromosomal. In addition, these amplified DNA's were shown to be circular on the basis of their resistance to exonuclease III digestion and their behavior on OFAGE. Their mobility was also greatly changed after treatment with topoisomerase II, suggesting that the amplified DNA's were either supercoiled or concatenated circles.

Cell Line↗

Conjugal transfer of the gonococcal penicillinase plasmid.

Certain gonococci, which heretofore have lacked a conjugal mating system, can sexually transfer a small plasmid (4.5 x 10)6) daltons) which carries the gene for beta-lactamase production. Frequencies of conjugal transfer were similar into diverse recipients (other gonococci, Neisseria flava, and Escherichia coli), which suggests that gonococci may transfer the plasmid promiscuously in nature.

Conjugation, Genetic↗

Interbacterial transfer of Escherichia coli--Drosophila melanogaster Recombinant plasmids.

Recombinants were constructed between various Escherichia coli plasmids and fragments of Drosophila melanogaster DNA. These recombinant plasmids are nonconjugative, but can be mobilized from one cell to another by conjugative sex factors. Of 47 recombinants studied, 46 were mobilized at approximately the same or slightly lower frequencies than the parental plasmids, whereas one was mobilized 1000 times less efficiently.

Conjugation, Genetic↗

Nucleotide sequences from a rabbit alpha globin gene inserted in a chimeric plasmid.

Rabbit alpha globin gene copies have been made, using reverse transcriptase and DNA polymerase I, and cloned in bacterial plasmids. Plasmid pHb72 has been shown to contain the alpha gene sequence by restriction enzyme analysis and nucleotide sequencing studies, and therefore has been approved for propagation under P2 plus EK1 conditions by the National REcombinant DNA Committee.

Base Sequence↗

Probability of establishing chimeric plasmids in natural populations of bacteria.

Formulas for estimating the probability that chimeric plasmids carried by disarmed hosts will become established in natural populations of bacteria are presented and their use illustrated with a series of realistic numerical examples. The implications of these a priori probability estimates for the problem of containment for recombinant DNA research is discussed.

Conjugation, Genetic↗