What is the purpose of Southern blotting?

The primary purpose of Southern blotting is to detect and analyze specific DNA sequences within a sample (blood or tissue). This allows researchers to determine whether certain DNA sequences are present or not. Southern blot is also used to investigate genetic mutations, such as deletions, insertions, duplications or rearrangements by comparing the DNA fragment patterns between samples. For example, it can be used for detecting deletions in cancerous cells or be used to diagnose genetic diseases (e.g. myotonic dystrophy type 1). Southern blotting is also used for determining the size of DNA fragments containing the target sequence and quantifying their abundance. Additionally, Southern blotting is used for assessing the gene copy count in a tissue sample. Southern blotting also plays a significant role in the creation of restriction enzyme maps. Based on the positions of restriction sites identified on the Southern blot, researchers can make a restriction enzyme map for the target DNA sequence.