scholarly journals Distribution of Chi-stimulated recombinational exchanges and heteroduplex endpoints in phage lambda.

Genetics ◽  
1989 ◽  
Vol 123 (1) ◽  
pp. 5-17 ◽  
Author(s):  
K C Cheng ◽  
G R Smith
Keyword(s):  
Phage Lambda ◽  
Heteroduplex Dna ◽  
Single Base ◽  
Chi Sequence ◽  
Mismatch Correction ◽  
Single Base Pair ◽  
The Right ◽  
Recombination Pathway ◽  
Recbcd Enzyme ◽  
Lambda Phages

Abstract The recombination hotspot Chi, 5' G-C-T-G-G-T-G-G 3', stimulates the RecBCD recombination pathway of Escherichia coli. We have determined, with precision greater than previously reported, the distribution of Chi-stimulated exchanges around a Chi site in phage lambda. Crosses of lambda phages with single base-pair mutations surrounding a Chi site were conducted in and analyzed on mismatch correction-impaired hosts to preserve heteroduplex mismatches for analysis. Among phages recombinant for flanking markers, Chi stimulated exchanges most intensely in the intervals immediately adjacent to the Chi site, both to its right and to its left. Stimulation fell off abruptly to the right but gradually to the left (with respect to the orientation of the Chi sequence written above). We have also determined that Chi stimulated the formation of heteroduplex DNA, which frequently had one endpoint to the right of Chi and the other endpoint to the left. These data support a model of Chi-stimulated recombination in which RecBCD enzyme cuts DNA immediately to the right of Chi and unwinds DNA to the left of Chi; segments of unwound single-stranded DNA are sometimes, but not always, degraded before synapsis with homologous DNA.

scholarly journals Heteroduplex chain polarity in recombination of phage lambda by the red, RecBCD, RecBC(D-) and RecF pathways.

Genetics ◽  
1991 ◽  
Vol 128 (1) ◽  
pp. 7-22 ◽  
Author(s):  
I Siddiqi ◽  
M M Stahl ◽  
F W Stahl
Keyword(s):  
Escherichia Coli ◽  
Genetic Map ◽  
Bacteriophage Lambda ◽  
The Other ◽  
Genetic Contribution ◽  
Phage Lambda ◽  
Heteroduplex Dna ◽  
Recf Pathway ◽  
The Right ◽  
Parental Information

Abstract We have examined the chain polarity of heteroduplex DNA in unreplicated, bacteriophage lambda splice recombinants when recombination was by the RecBCD, RecBC(D-), or RecF pathway of Escherichia coli or the Red pathway of lambda. For each of these pathways, recombination is activated by the cutting of cos that accompanies chromosome packaging, and is effected by recombination enzymes acting at the right end created by that cutting. For exchanges occurring near cos, one parent makes a lesser physical and genetic contribution than does the other. For each pathway, when the phage carried standard cos, this minority contribution was predominantly on the r chain, ending 5' at the right end of lambda. When standard cos was replaced by a cloned inverted cos located centrally on the standard lambda genetic map, minority contribution was predominantly on the l chain. In each case, the polarity of the overlap was usually that formed by 3' overhangs of parental information and material. These results are discussed in the context of current models of recombination for the different pathways.

scholarly journals Repair of heteroduplex DNA in Xenopus laevis oocytes.

Genetics ◽  
1994 ◽  
Vol 138 (2) ◽  
pp. 459-470 ◽  
Author(s):  
C W Lehman ◽  
S Jeong-Yu ◽  
J K Trautman ◽  
D Carroll
Keyword(s):  
Xenopus Laevis ◽  
Xenopus Oocytes ◽  
Blot Hybridization ◽  
Southern Blot Hybridization ◽  
Xenopus Laevis Oocytes ◽  
Heteroduplex Dna ◽  
Strand Breaks ◽  
Single Base ◽  
Mismatch Correction

Abstract We have hypothesized that the inheritance of heteroallelic markers during recombination of homologous DNAs in Xenopus oocytes is determined by resolution of a heteroduplex intermediate containing multiple single-base mismatches. To test this idea, we prepared synthetic heteroduplexes carrying 8 separate mispairs in vitro and injected them into oocyte nuclei. DNA was recovered and analyzed directly, by Southern blot-hybridization, and indirectly, by cloning individual repair products in bacteria. Mismatch correction was quite efficient in the oocytes; markers on the same strand were commonly co-corrected, indicating a long-patch mechanism; and the distribution of markers was very similar to that obtained by recombination. This supports our interpretation of the recombination outcome in terms of a resection-annealing mechanism. The injected heteroduplexes carried strand breaks (nicks) as a result of their method of preparation. We tested the idea that mismatch correction might be nick-directed by ligating the strands of the heteroduplex substrate to form covalently closed circles. Repair in oocytes was still efficient, and long patches predominated; but the pattern of recovered markers was quite different than with the nicked substrate. This suggests that nicks, when present, do indeed direct repair, but that, in their absence, recognition of specific mismatches governs repair of the ligated heteroduplexes.

scholarly journals Effect of the Molecular Nature of Mutation on the Efficiency of Intrachromosomal Gene Conversion in Mouse Cells

Genetics ◽  
1987 ◽  
Vol 117 (4) ◽  
pp. 759-769
Author(s):  
Anthea Letsou ◽  
R Michael Liskay
Keyword(s):  
Gene Conversion ◽  
Mammalian Cells ◽  
Directed Path ◽  
Wild Type ◽  
Heteroduplex Dna ◽  
Single Base ◽  
Conversion Rates ◽  
Mouse Cells ◽  
Single Base Pair ◽  
Molecular Nature

ABSTRACT With the intent of further exploring the nature of gene conversion in mammalian cells, we systematically addressed the effects of the molecular nature of mutation on the efficiency of intrachromosomal gene conversion in cultured mouse cells. Comparison of conversion rates revealed that all mutations studied were suitable substrates for gene conversion; however, we observed that the rates at which different mutations converted to wild-type could differ by two orders of magnitude. Differences in conversion rates were correlated with the molecular nature of the mutations. In general, rates of conversion decreased with increasing size of the molecular lesions. In comparisons of conversion rates for single base pair insertions and deletions we detected a genotype-directed path for conversion, by which an insertion was converted to wild-type three to four times more efficiently than was a deletion which maps to the same site. The data are discussed in relation to current theories of gene conversion, and are consistent with the idea that gene conversion in mammalian cells can result from repair of heteroduplex DNA (hDNA) intermediates.

Large non-homology in heteroduplex DNA is processed differently than single base pair mismatches

1987 ◽  
Vol 206 (1) ◽  
pp. 181-184 ◽  
Author(s):  
C. Dohet ◽  
S. Džidić ◽  
R. Wagner ◽  
M. Radman
Keyword(s):  
Base Pair ◽  
Heteroduplex Dna ◽  
Single Base ◽  
Single Base Pair

scholarly journals Overexpression of the MtrC-MtrD-MtrE Efflux Pump Due to an mtrR Mutation Is Required for Chromosomally Mediated Penicillin Resistance in Neisseria gonorrhoeae

2002 ◽  
Vol 184 (20) ◽  
pp. 5619-5624 ◽  
Author(s):  
Wendy L. Veal ◽  
Robert A. Nicholas ◽  
William M. Shafer
Keyword(s):  
Neisseria Gonorrhoeae ◽  
Base Pair ◽  
Efflux Pump ◽  
Penicillin Resistance ◽  
Single Base ◽  
Base Pair Deletion ◽  
Resistance To Penicillin ◽  
Single Base Pair ◽  
High Level ◽  
Level Resistance

ABSTRACT The importance of the mtrCDE-encoded efflux pump in conferring chromosomally mediated penicillin resistance on certain strains of Neisseria gonorrhoeae was determined by using genetic derivatives of penicillin-sensitive strain FA19 bearing defined mutations (mtrR, penA, and penB) donated by a clinical isolate (FA6140) expressing high-level resistance to penicillin and antimicrobial hydrophobic agents (HAs). When introduced into strain FA19 by transformation, a single base pair deletion in the mtrR promoter sequence from strain FA6140 was sufficient to provide high-level resistance to HAs (e.g., erythromycin and Triton X-100) but only a twofold increase in resistance to penicillin. When subsequent mutations in penA and porIB were introduced from strain FA6140 into strain WV30 (FA19 mtrR) by transformation, resistance to penicillin increased incrementally up to a MIC of 1.0 μg/ml. Insertional inactivation of the gene (mtrD) encoding the membrane transporter component of the Mtr efflux pump in these transformant strains and in strain FA6140 decreased the MIC of penicillin by 16-fold. Genetic analyses revealed that mtrR mutations, such as the single base pair deletion in its promoter, are needed for phenotypic expression of penicillin and tetracycline resistance afforded by the penB mutation. As penB represents amino acid substitutions within the third loop of the outer membrane PorIB protein that modulate entry of penicillin and tetracycline, the results presented herein suggest that PorIB and the MtrC-MtrD-MtrE efflux pump act synergistically to confer resistance to these antibiotics.

Dinucleotide microsatellites from Eucalyptus sieberi: inheritance, diversity, and improved scoring of single-base differences

Genome ◽  
2001 ◽  
Vol 44 (6) ◽  
pp. 1041-1045 ◽  
Author(s):  
J C Glaubitz ◽  
L C Emebiri ◽  
G F Moran
Keyword(s):  
Base Pair ◽  
Mendelian Inheritance ◽  
Null Alleles ◽  
Fixation Index ◽  
Eucalyptus Nitens ◽  
Internal Reference ◽  
Single Base ◽  
Hardy Weinberg Equilibrium ◽  
Single Base Pair ◽  
Flanking Regions

Eight dinucleotide microsatellites were developed in Eucalyptus sieberi L. Johnson (silvertop ash), a member of the subgenus Eucalyptus. Transfer of six of these to the subgenus Symphyomyrtus and their Mendelian inheritance are demonstrated using a full-sib cross in Eucalyptus nitens. Genetic diversity parameters are presented for the eight loci based on a sample of 100 old-growth E. sieberi trees from a single natural stand. One locus, Es266, had an atypically high fixation index, and significantly deviated from Hardy-Weinberg equilibrium genotypic proportions, indicating the likely presence of null alleles. Two of the loci, Es076 and Es140, had many alleles that differed in size by only a single base pair, possibly because of short poly(A) or poly(T) stretches in their flanking regions. These two loci were by far the most polymorphic, but were difficult to score reliably on a capillary DNA sequencer. Reliability of scoring of these two one-base microsatellite loci was markedly improved by the incorporation of internal reference alleles into each sample analysed.Key words: SSRs, single base pair alleles, null alleles, internal reference alleles.

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