Question

The term 'southern blotting' refers to

• A. Transfer of DNA fragments from in vitro cellulose membrane to electrophoresis gel
• B. Attachment of probes to DNA fragments
• C. Transfer of DNA fragments from electrophoresis gel to nitrocellulose sheet
• D. Comparison of DNA fragments from two sources

Answer 1

Answer: (C)

Transfer of DNA fragments from electrophoresis gel to nitrocellulose sheet

Southern blotting is used to detect specific DNA sequence in a given sample of DNA. The first step in a Southern blot is to prepare the DNA mixture by breaking it into small fragments using a restriction enzyme. The mixture of DNA fragments is then separated according to size by gel electrophoresis. Then the double-stranded pieces of DNA are denatured into single strands within the gel. Next, the DNA is transferred from the gel onto a blotting membrane called the nitrocellulose membrane. The DNA is labeled using radioactive probes that can be detected by autoradiography. Thus the correct answer is option C.