Many of the gene products involved in DNA synthesis were initially defined by studying mutant E. coli strains that could not synthesize DNA.
The dnaQ gene encodes the ε subunit of DNA polymerase. What effect is expected from a mutation in this gene?

Verified step by step guidance

1. Understand the role of the dnaQ gene: It encodes the ε (epsilon) subunit of DNA polymerase III in E. coli, which is responsible for the proofreading activity during DNA replication.
2. Recall that the ε subunit has 3' to 5' exonuclease activity, which means it can remove incorrectly incorporated nucleotides, ensuring high fidelity of DNA synthesis.
3. Predict the effect of a mutation in the dnaQ gene: If the ε subunit is defective or missing, the proofreading function will be impaired, leading to an increase in replication errors.
4. Consider the biological consequence: Without proper proofreading, the mutation rate during DNA replication will increase, potentially causing accumulation of mutations in the bacterial genome.
5. Summarize that a mutation in dnaQ is expected to reduce the accuracy of DNA synthesis by compromising the proofreading ability of DNA polymerase III.

Key Concepts

Role of DNA Polymerase in DNA Synthesis

DNA polymerase is the enzyme responsible for synthesizing new DNA strands by adding nucleotides complementary to the template strand. It ensures accurate replication of the genome during cell division, with multiple subunits contributing to its function.

Function of the ε Subunit (dnaQ Gene Product)

The ε subunit of DNA polymerase, encoded by the dnaQ gene, provides 3' to 5' exonuclease proofreading activity. This function corrects errors by removing incorrectly incorporated nucleotides, thereby increasing the fidelity of DNA replication.

Effects of Mutations in dnaQ on DNA Replication

Mutations in the dnaQ gene impair the proofreading ability of DNA polymerase, leading to increased replication errors and higher mutation rates. Such defects can cause genomic instability and affect cell viability or function.