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Genetic deletions between directly repeated sequences in bacteriophage T7
1Department of Biochemistry, Temple University School of Medicine, Philadelphia, PA 19140.
Molecular & General Genetics : MGG
|June 1, 1989
Summary
Genetic deletions in bacteriophage T7 DNA are sensitive to repeat length. Shorter direct repeats (5 bp) resulted in extremely low deletion frequencies (<10(-10)), while longer repeats (10 bp) showed higher excision rates (~10(-6)).
Area of Science:
- Molecular Biology
- Genetics
- Virology
Background:
- Chromosomal rearrangements, specifically genetic deletions in bacteriophage T7, are known to occur frequently between directly repeated DNA sequences.
- Understanding the mechanisms and quantitative details of these spontaneous deletions is crucial for comprehending genome stability.
Purpose of the Study:
- To quantitatively investigate spontaneous deletion events in bacteriophage T7 DNA.
- To determine the influence of direct repeat length on the frequency of DNA insert excision.
Main Methods:
- Introduction of synthetic DNA fragments, synthesized by hybridizing complementary oligonucleotides, into the non-essential T7 gene 1.3.
- Designing inserts flanked by direct repeats, where precise deletion restores wild-type phage functionality.
- Assessing deletion frequency by plaque assays on a host strain deficient in bacterial ligase, with deletion events independent of host recA mutation.
Main Results:
- Deletion events are highly sensitive to the length of the flanking direct repeats.
- A 5 bp direct repeat resulted in an excision frequency below 10(-10).
- An almost identical insert with 10 bp direct repeats exhibited an excision frequency of approximately 10(-6).
Conclusions:
- The length of direct repeats significantly impacts the frequency of spontaneous DNA deletion in bacteriophage T7.
- This study provides quantitative data on the relationship between direct repeat length and deletion efficiency, offering insights into DNA repair mechanisms.