What happens when DNA is cross-linked by platinum compounds?

When platinum compounds cross-link DNA, they form covalent bonds between DNA strands, which significantly disrupts the normal processes of DNA replication and transcription. This cross-linking creates physical barriers to these processes, leading to the stalling of the DNA replication fork. Consequently, the cell detects the damage and responds by activating checkpoints in the cell cycle.

As a result, the cell cycle is arrested to provide time for DNA repair mechanisms to engage and attempt to resolve the damage caused by the cross-linking. If the damage is irreparable, this can lead to further cellular responses, such as apoptosis. However, at the point of cross-linking, the primary immediate effect is the arrest of the cell cycle, which prevents the cell from proceeding to complete division, allowing it to either repair itself or, if the damage is too severe, undergo programmed cell death. This is why the correct answer focuses on the arresting of the cell cycle in response to DNA damage caused by platinum compounds.