Final answer:
Homologous recombination is the repair mechanism for double-strand breaks in DNA just after replication, using sister chromatids to maintain genetic integrity.
Step-by-step explanation:
The correct answer to the question of what type of repair mechanism is used for a double-strand break that occurs just after replication in an actively dividing cell is C) Homologous recombination.This repair mechanism relies on the fact that double-stranded DNA shows a specific pattern of methylation. When DNA replicates, the methyl groups on the template DNA strands remain, but the newly synthesized DNA is unmethylated. In the intervening time, several proteins and enzymes can detect inappropriate base pairing (the mismatches) and initiate mismatch repair.
In an actively dividing cell, once DNA replication occurs, the newly formed sister chromatids are in close proximity, which is ideal for homologous recombination to occur. Homologous recombination is a repair process that uses the undamaged sister chromatid as a template to accurately repair the break without any deletions or loss of genetic information. This process is critical for maintaining the integrity of the genome and preventing mutations or chromosome rearrangements that could lead to cell dysfunction or death.