Final answer:
The purpose of denaturation of DNA after electrophoresis in Southern blotting is to convert double-stranded DNA to single-stranded DNA, which allows for the hybridization of the DNA probe to specific DNA sequences on the membrane.
Step-by-step explanation:
The purpose of denaturation of double-stranded target DNA after electrophoresis and prior to transfer in Southern blot is to make the DNA single-stranded. This is necessary for the DNA probe to hybridize with the target sequence. During Southern blotting, after separation of DNA fragments by agarose gel electrophoresis, the transferred fragments on the membrane must be single-stranded to allow the DNA probe, which is also single-stranded and labeled with a radioactive or fluorescent molecular beacon, to anneal specifically to complementary DNA sequences of interest. Since double-stranded DNA will not allow for proper probe binding, denaturation is a crucial step to ensure the specific and effective hybridization between the probe and the target DNA sequence.