Question

In order for mismatch repair to occur in a bacterial cell, the enzyme machinery must be able to Blank______.

Multiple choice question.
A. block replication from occurring until the mismatch repair is completed
B. efficiently find thymine dimers along the DNA strand
C. distinguish between the template strand and a newly synthesized strand

Answer 1

Mismatch repair machinery in bacterial cells like E. coli distinguishes between the old and new DNA strands by methylation patterns. The parental strand's methylation guides repair enzymes to the newly synthesized strand where the mismatch is corrected.

Step-by-step explanation:

In order for mismatch repair to occur in a bacterial cell, the enzyme machinery must be able to distinguish between the template strand and a newly synthesized strand. When DNA in bacteria such as E. coli replicates, the original DNA strand is methylated, whereas the newly synthesized strand is not immediately methylated. This difference allows repair enzymes to identify which strand contains the error. Proteins such as Muts, MutL, and MutH bind to the hemimethylated sites of DNA. Specifically, MutH recognizes and cuts the unmethylated strand, which is the newer strand. An exonuclease then removes a section of the DNA containing the incorrect nucleotide, and DNA polymerase III fills in the gap with the correct bases. Finally, DNA ligase seals the strand, completing the repair process.