Question

Arrange the following steps of DNA fingerprinting in correct sequence: 
(a) Gel electrophoresis (b) Isolation of DNA (c) Southern blotting (d) Restriction digestion

Hint:

DNA fingerprinting, pivotal in forensics and genetic analysis, was pioneered by Alec Jeffreys in 1984. It remains essential for verifying genetic relationships and solving criminal cases.

Answer 1

DNA fingerprinting is a method utilized for identifying individuals by analyzing their distinctive DNA sequences. The accurate sequence of steps in DNA fingerprinting includes: 
1. DNA Isolation (Step - b): DNA is isolated from sources such as blood, hair roots, or saliva through chemical processes that disrupt cell membranes. 
2. Restriction Digestion (Step - d): Specific restriction enzymes are used to cut the isolated DNA at precise sequences, resulting in fragments of varying lengths. 
3. Gel Electrophoresis (Step - a): These DNA fragments are sorted by size using agarose gel electrophoresis, where negatively charged DNA moves towards the positive electrode, allowing smaller fragments to travel faster. 
4. Southern Blotting (Step - c): The DNA fragments are then blotted onto a nylon membrane from the gel, and specific sequences are identified using a radioactive or fluorescent DNA probe. 
5. Visualization and Analysis (Step - not listed but essential): DNA patterns are revealed through autoradiography on X-ray film, creating a DNA fingerprint used in forensic science, paternity tests, and genetic research.

(b) Isolation of DNA → (d) Restriction digestion → (a) Gel electrophoresis → (c) Southern blotting