TY - JOUR
T1 - Tandem genetic duplications in phage lambda. III. The frequency of duplication mutants in two derivatives of phage lambda is independent of known recombination systems
AU - Emmons, Scott W.
AU - MacCosham, Virginia
AU - Baldwin, Robert L.
N1 - Funding Information:
The authors thank Drs N. C. Franklin and A. D. Kaiser for their thoughtful criticism of the manuscript. This work was supported by research grants from the U.S. National Institutes of Health (grant GMAM19,983-13) and National Science Foundation (grant GB-36432X) to one author (R. L. B.). Another author (S. E.) is a U.S. Public Health Service predoctoral trainee.
PY - 1975/1/15
Y1 - 1975/1/15
N2 - The rate of production of tandem duplications in phage λ has been measured in the presence and absence of known recombination systems. Two deletion phages have been used: tdel33, a deletion derivative of a φ80-λ hybrid phage, and λb221, which carries a large deletion of the central portion of the λ chromosome. Both phages are int-, and tdel33 is also red-, by virtue of their deletions. Stocks of these phages can be prepared free of long tandem duplication derivatives by CsCl density gradient purification. After a single cycle of lytic growth, lysates from these purified phage stocks contain tandem duplications at a frequency of 10-3 in the case of tdel33 and 10-5 in the case of λb221. These frequencies are unaffected by the presence of mutations in the host Rec system or the phage Red system. To investigate the difference in duplication frequency between tdel33 and λb221, the phages were grown in mixed infection. The result indicates that a trans-active product of tdel33 is responsible for its high frequency of duplication production. Tandem duplications have been detected by banding the phage lysates in CsCl density gradients. Long DNA addition mutants can be detected in this way if they arise with a frequency of at least 10-5 and if the duplication length is at least 0.14 λ lengths. To accomplish this it is necessary to distinguish them from contaminating parental phage and from dense phages with aberrant structures which arise at roughly comparable frequencies. The former can be done by rebanding and the latter by growth and rebanding. To distinguish these types we have also made use of a new mutant of Escherichia coli which does not plate λ deletion phages. All of the DNA addition mutants we have detected in this way are tandem duplications; evidently mutants with long insertions arise more rarely.
AB - The rate of production of tandem duplications in phage λ has been measured in the presence and absence of known recombination systems. Two deletion phages have been used: tdel33, a deletion derivative of a φ80-λ hybrid phage, and λb221, which carries a large deletion of the central portion of the λ chromosome. Both phages are int-, and tdel33 is also red-, by virtue of their deletions. Stocks of these phages can be prepared free of long tandem duplication derivatives by CsCl density gradient purification. After a single cycle of lytic growth, lysates from these purified phage stocks contain tandem duplications at a frequency of 10-3 in the case of tdel33 and 10-5 in the case of λb221. These frequencies are unaffected by the presence of mutations in the host Rec system or the phage Red system. To investigate the difference in duplication frequency between tdel33 and λb221, the phages were grown in mixed infection. The result indicates that a trans-active product of tdel33 is responsible for its high frequency of duplication production. Tandem duplications have been detected by banding the phage lysates in CsCl density gradients. Long DNA addition mutants can be detected in this way if they arise with a frequency of at least 10-5 and if the duplication length is at least 0.14 λ lengths. To accomplish this it is necessary to distinguish them from contaminating parental phage and from dense phages with aberrant structures which arise at roughly comparable frequencies. The former can be done by rebanding and the latter by growth and rebanding. To distinguish these types we have also made use of a new mutant of Escherichia coli which does not plate λ deletion phages. All of the DNA addition mutants we have detected in this way are tandem duplications; evidently mutants with long insertions arise more rarely.
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U2 - 10.1016/0022-2836(75)90154-0
DO - 10.1016/0022-2836(75)90154-0
M3 - Article
C2 - 1102698
AN - SCOPUS:0016441810
SN - 0022-2836
VL - 91
SP - 133
EP - 146
JO - Journal of Molecular Biology
JF - Journal of Molecular Biology
IS - 2
ER -