What is southern blot as a part of the gel electrophoresis process? and what does it tell you?

I think the answer for this Question is DNA

The truman doctrine was an american foreign policy whose stated purpose was to counter soviet geopolitical expansion during the cold war. it was announced to congress by president harry s. truman on march 12, 1947, and further developed on july 12, 1948, when he pledged to contain threats to greece and turkey