scholarly journals Effects of DNA heterologies on bacteriophage lambda recombination.

Genetics ◽  
1988 ◽  
Vol 118 (1) ◽  
pp. 13-19
Author(s):  
R K Pearson ◽  
M S Fox
Keyword(s):  
Bacteriophage Lambda ◽  
Indirect Evidence ◽  
Direct Products ◽  
Base Pairs ◽  
Heteroduplex Dna ◽  
Deletion Mutations ◽  
Genetic Crosses ◽  
Insertion And Deletion ◽  
Progeny Phage ◽  
Substitution Mutation

Abstract Previous studies of bacteriophage lambda recombination have provided indirect evidence that substantial sequence nonhomologies, such as insertions and deletions, may be included in regions of heteroduplex DNA. However, the direct products of heterology-containing heteroduplex DNA--heterozygous progeny phage--have not been observed. We have constructed a series of small insertion and deletion mutations in the cI gene to examine the possibility that small heterologies might be accommodated in heterozygous progeny phage. Genetic crosses were carried out between lambda cI- Oam29 and lambda cI+ Pam80 under replication-restricted conditions. Recombinant O+P+ progeny were selected on mutL hosts and tested for cI heterozygosity. Heterozygous recombinants were readily observed with crosses involving insertions of 4 to 19 base pairs (bp) in the cI gene. Thus, nonhomologies of at least 19 bp can be accommodated in regions of heteroduplex DNA during lambda recombination. In contrast, when a cI insertion or deletion mutation of 26 bp was present, few of the selected recombinants were heterozygous for cI. Results using a substitution mutation, involving a 26-bp deletion with a 22-bp insertion, suggest that the low recovery of cI heterozygotes containing heterologies of 26 bp or more is due to a failure to encapsulate DNA containing heterologies of 26 bp or more into viable phage particles.

Timing of molecular events in meiosis in Saccharomyces cerevisiae: stable heteroduplex DNA is formed late in meiotic prophase

1993 ◽  
Vol 13 (1) ◽  
pp. 373-382 ◽  
Author(s):  
C Goyon ◽  
M Lichten
Keyword(s):  
Meiotic Prophase ◽  
Double Strand Breaks ◽  
Dna Breaks ◽  
Base Pairs ◽  
Heteroduplex Dna ◽  
Strand Breaks ◽  
Dna Structures ◽  
Double Strand Dna Breaks ◽  
Molecular Events ◽  
The Times

To better understand the means by which chromosomes pair and recombine during meiosis, we have determined the time of appearance of heteroduplex DNA relative to the times of appearance of double-strand DNA breaks and of mature recombined molecules. Site-specific double-strand breaks appeared early in meiosis and were formed and repaired with a timing consistent with a role for breaks as initiators of recombination. Heteroduplex-containing molecules appeared about 1 h after double-strand breaks and were followed shortly by crossover products and the first meiotic nuclear division. We conclude that parental chromosomes are stably joined in heteroduplex-containing structures late in meiotic prophase and that these structures are rapidly resolved to yield mature crossover products. If the chromosome pairing and synapsis observed earlier in meiotic prophase is mediated by formation of biparental DNA structures, these structures most likely either contain regions of non-Watson-Crick base pairs or contain regions of heteroduplex DNA that either are very short or dissociate during DNA purification. Two loci were examined in this study: the normal ARG4 locus, and an artificial locus consisting of an arg4-containing plasmid inserted at MAT. Remarkably, sequences in the ARG4 promoter that suffered double-strand cleavage at the normal ARG4 locus were not cut at significant levels when present at MAT::arg4. These results indicate that the formation of double-strand breaks during meiosis does not simply involve the specific recognition and cleavage of a short nucleotide sequence.

Deletion mutants which affect the nuclease-sensitive site in simian virus 40 chromatin

1982 ◽  
Vol 2 (7) ◽  
pp. 782-788
Author(s):  
R D Gerard ◽  
M Woodworth-Gutai ◽  
W A Scott
Keyword(s):  
Simian Virus 40 ◽  
Simian Virus ◽  
Deletion Mutants ◽  
Sequence Information ◽  
Base Pairs ◽  
Deletion Mutations ◽  
Sensitive Site ◽  
Late Side ◽  
Nuclease Sensitivity

A short segment of simian virus 40 (SV40) chromatin on the late side of the origin of replication is hypersensitive to nuclease cleavage. The role of DNA sequence information in this nuclease-sensitive feature was examined by constructing deletion mutations in this region. Deletions were introduced into the inserted segment of in(Or)-1411 (a viable, partially duplicated variant of SV40), and nuclease sensitivity of the inserted segment was compared with that of the unaltered sequences in their normal location in the viral genome. Extended deletions (118 to 161 base pairs) essentially abolished nuclease sensitivity within the inserted segment. Shorter deletions (21 to 52 base pairs) at separate locations retained the nuclease-sensitive feature. In some short-deletion mutants nuclease susceptibility was substantially reduced. We conclude that more than one genetic element in this region contributes to the organization of the nuclease-sensitive feature and that the SV40 72-base repeat is not, in itself, sufficient signal for this feature.

scholarly journals A DNA sequence conferring high postmeiotic segregation frequency to heterozygous deletions in Saccharomyces cerevisiae is related to sequences associated with eucaryotic recombination hotspots.

1988 ◽  
Vol 8 (3) ◽  
pp. 1253-1258 ◽  
Author(s):  
J H White ◽  
J F DiMartino ◽  
R W Anderson ◽  
K Lusnak ◽  
D Hilbert ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Molecular Basis ◽  
The Novel ◽  
Joint Region ◽  
Base Pairs ◽  
Deletion Mutations ◽  
Recombination Hotspots ◽  
Postmeiotic Segregation ◽  
Human And Mouse ◽  
Common Sequence

The meiotic behavior of two graded series of deletion mutations in the ADE8 gene in Saccharomyces cerevisiae was analyzed to investigate the molecular basis of meiotic recombination. Postmeiotic segregation (PMS) was observed for a subset of the deletion heterozygosities, including deletions of 38 to 93 base pairs. There was no clear relationship between deletion length and PMS frequency. A common sequence characterized the novel joint region in the alleles which displayed PMS. This sequence is related to repeated sequences recently identified in association with recombination hotspots in the human and mouse genomes. We propose that these particular deletion heterozygosities escape heteroduplex DNA repair because of fortuitous homology to a binding site for a protein.

scholarly journals Base insertion and deletion mutations induced in an Escherichia coli plasmid by benzo[a]pyrene-7,8-dihydrodiol-9,10-epoxide.

1981 ◽  
Vol 78 (11) ◽  
pp. 6817-6820 ◽  
Author(s):  
H. Mizusawa ◽  
C. H. Lee ◽  
T. Kakefuda ◽  
K. McKenney ◽  
H. Shimatake ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Deletion Mutations ◽  
Insertion And Deletion ◽  
Coli Plasmid ◽  
Base Insertion

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.

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