Question

What is the first step in the Southern Blot technique?

• A. Denaturation of DNA on the gel for hybridization with specific probe
• B. Production of a group of genetically identical cells
• C. Digestion of DNA by restriction enzyme
• D. Isolation of DNA from a nucleated cell such as the one from the scene of crime

Answer 1

Answer: (D)

Isolation of DNA from a nucleated cell such as the one from the scene of crime

Answer 2

A Southern blot is a method used for detection of a specific DNA sequence in DNA samples. This method combines transfer of electrophoresis-separated DNA fragments to a filter membrane and subsequent fragment detection by probe hybridization. The first step in a Southern blot is to isolate the DNA from the cells collected from the crime scene. The next step would be to prepare the DNA mixture by breaking it into small fragments using a protein called a restriction enzyme. The mixture of DNA fragments is then separated according to size by way of a technique called gel electrophoresis. Following separation, the double-stranded pieces of DNA are denatured, or separated, into single strands within the gel. Next, the DNA is transferred from the gel onto a blotting membrane. This step is what gives the technique the name Southern blotting So, the correct answer is 'Isolation of DNA from a nucleated cell such as the one from the scene of crime'