Several temperature-sensitive mutant strains of E. coli display the following characteristics. Predict what enzyme or function is being affected by each mutation. Okazaki fragments accumulate, and DNA synthesis is never completed.

Key Concepts

Okazaki Fragments

Okazaki fragments are short sequences of DNA synthesized on the lagging strand during DNA replication. They are formed because DNA polymerase can only synthesize DNA in the 5' to 3' direction, necessitating the creation of these fragments as the replication fork opens. Understanding their formation is crucial for analyzing mutations that affect DNA synthesis.

DNA Polymerase

DNA polymerase is the enzyme responsible for synthesizing new DNA strands by adding nucleotides complementary to the template strand. In E. coli, DNA polymerase III is the primary enzyme for elongating the new DNA strand. Mutations affecting this enzyme can lead to incomplete DNA synthesis, as seen with the accumulation of Okazaki fragments.

Temperature-Sensitive Mutants

Temperature-sensitive mutants are organisms that exhibit normal function at one temperature but show a defect at a different temperature. In the context of E. coli, these mutations can affect enzymes like DNA polymerase, leading to issues in DNA replication at non-permissive temperatures. This concept is essential for predicting the effects of specific mutations on cellular functions.