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Studies on bacteriophage M13 DNA. 2. The gene order of the M13 genome
Abstract:
The double-stranded replicative form DNA of bacteriophage M13 was cleaved into 13 specific fragments by the restriction endonuclease from Haemophilus aphirophilus. The individual DNA fragments from wild-type replicative form molecules were then annealed to circular, single-stranded DNAs of phage M13, bearing amber mutations as genetic markers. When such DNA hybrids infected competent Escherichia coli cells, only those duplexes which were genetically heterozygous gave rise to wild-type phages in the progeny. In this way, the genetic markers carried on the individual DNA fragments could be determined. In addition, marker rescue in each gene was obtained with the 10 specific fragments of M13 replicative form DNA, produced by cleavage with the restriction endonuclease from Haemophilus aegyptius. From these results and the enzyme cleavage maps of both types of restriction fragments a distribution of genetic markers along the physical map could be obtained, which allowed an arrangement of M13 genes into a genetic map. Evidence is presented that the gene order of M13 is: IV-(I,VI)-III-VIII-VII-V-II with II and IV being contiguous on the circular map.
Insights
Researchers mapped bacteriophage M13 genes using DNA fragment analysis. This method determined the genetic order of M13 genes, revealing specific gene arrangements on the circular DNA map.
Area of Science:
- Molecular Biology
- Genetics
- Virology
Background:
- Bacteriophage M13 is a vital model organism for DNA replication studies.
- Understanding bacteriophage M13 gene organization is crucial for molecular biology research.
Purpose of the Study:
- To construct a genetic map of bacteriophage M13.
- To determine the precise arrangement of genes on the M13 genome.
Main Methods:
- Cleavage of M13 replicative form DNA using restriction endonucleases (Haemophilus aphirophilus and H. aegyptius).
- Annealing of DNA fragments to single-stranded M13 DNA with amber mutations.
- Infection of Escherichia coli with DNA hybrids to identify heterozygous duplexes and determine genetic markers.
- Marker rescue experiments using specific DNA fragments.
Main Results:
- Successfully mapped genetic markers to specific DNA fragments.
- Established the gene order of M13 as IV-(I,VI)-III-VIII-VII-V-II.
- Demonstrated that genes II and IV are contiguous on the circular map.
Conclusions:
- Developed a method for bacteriophage M13 gene mapping using restriction fragment analysis.
- Provided a detailed genetic map of bacteriophage M13, elucidating gene order and arrangement.
- This genetic map serves as a foundational resource for future M13-based research.