Final answer:
The DNA polymerase in bacteria that has not yet had a function assigned to it is DNA polymerase II. In a cell strain with impaired joining of Okazaki fragments, the most likely mutated enzyme is DNA polymerase I.
Step-by-step explanation:
The DNA polymerase in bacteria that has not yet had a function assigned to it, since bacterial mutants for it have been isolated without seeming to have any evident deficiencies, is DNA polymerase II.
In prokaryotes, such as bacteria, there are three main types of DNA polymerases known: DNA polymerase I, II, and III. Among these, DNA polymerase III is the enzyme required for DNA synthesis, while DNA polymerase I and II are primarily involved in repair processes.
Therefore, the most likely enzyme to be mutated in a cell strain where the joining of Okazaki fragments is impaired is DNA polymerase I.