What are the advantages of southern blot over PCR?

Southern blotting provides a method for accurately sizing DNA repeat expansions that are too large to be amplified through PCR, as it does not rely on PCR amplification. Therefore, Southern blotting enables the detection and sizing of large DNA repeat expansions with precision. Southern blotting can be used to detect DNA methylation patterns, which PCR alone cannot accomplish without additional steps or modifications. Southern blotting can be used to detect specific DNA sequences regardless of their location within the genome. In contrast PCR requires prior knowledge of target sequences for primer design. Southern blotting does not involve DNA amplification steps, avoiding potential amplification biases that can occur in PCR.