Final answer:
A cell with an altered DNA sequence would initiate the DNA damage response, using mechanisms like proofreading during replication and mismatch repair after replication to correct errors and maintain genetic integrity.
Step-by-step explanation:
When a cell has an altered DNA sequence, the correct mechanism to address this problem is C. Initiate the DNA damage response. The DNA damage response involves a variety of repair mechanisms that cells utilize to correct errors. One such mechanism is proofreading by DNA polymerase during DNA replication. If an incorrect base has been added, the enzyme excises the wrong nucleotide and replaces it with the right one. Another mechanism is mismatch repair, which happens after DNA replication is completed, where repair enzymes recognize and fix incorrectly paired nucleotides.
Other mechanisms, like those that address pyrimidine dimers formed due to UV damage, involve excision nuclease that recognizes the damage and DNA polymerase and ligase that fill in and seal the gap, respectively. The ability of DNA to repair itself is vital for maintaining genetic integrity. Therefore, option C is the most fitting answer for how a cell might correct an altered DNA sequence.