Defined transversion mutations at a specific position in DNA using synthetic oligodeoxyribonucleotides as mutagens.

Area of Science:

• Molecular Biology
• Genetics
• Virology

Background:

• Bacteriophage phi X174 is a well-characterized model system for DNA replication and genetic studies.
• Specific nucleotide modifications are crucial for understanding gene function and viral evolution.

Purpose of the Study:

• To investigate the use of enzymatically synthesized oligodeoxynucleotides for targeted mutagenesis in bacteriophage phi X174.
• To establish a method for inducing specific single nucleotide replacements with high efficiency.

Main Methods:

• Synthesis of two complementary oligodeoxynucleotides, one with a specific base change.
• Primer extension using E. coli DNA polymerase I (Klenow enzyme) on wild-type phi X174 DNA template.
• Ligation, transfection of E. coli spheroplasts, and sequencing of mutated viral DNA.

Main Results:

• A G to A mismatch at nucleotide 5276 was created, leading to a G to T mutation in the viral DNA with 13% efficiency.
• The specific mutation (gene B mutant am16) was reverted to wild-type (T to G) using the wild-type oligonucleotide with 19% efficiency.
• Nucleotide sequence determination confirmed the specific transversion mutations induced.

Conclusions:

• Enzymatically synthesized oligodeoxynucleotides are effective tools for inducing specific single nucleotide replacements (transversions and transitions) in circular genomes.
• This technique provides a powerful and efficient method for targeted genetic manipulation in bacteriophage phi X174.
• The findings facilitate precise genetic engineering for studying gene function and viral biology.