Question

Arrange the below given steps of DNA fingerprinting in sequence by selecting the appropriate option.
a) Digestion of DNA by restriction endonucleases
b) Autoradiography
c) Blotting of DNA fragments to nitrocellulose membrane
d) Isolation of DNA
e) Separation of DNA fragments by electrophoresis

• A. (a), (e), (d), (c), (b)
• B. (e), (a), (d), (b), (c)
• C. (d), (a), (e), (c), (b)
• D. (c), (b), (a), (e), (d)

Hint:

Follow the logical physical flow: Isolate it $\rightarrow$ Cut it $\rightarrow$ Separate it $\rightarrow$ Transfer it $\rightarrow$ Photograph it.

Answer 1

The Correct Option is C

Step 1: Understanding the Problem:
DNA fingerprinting is a comprehensive forensic technique utilized to identify individuals based on variations in their DNA profiles, specifically by analyzing Variable Number of Tandem Repeats (VNTRs).
Step 2: Approach and Formula:
Logically sequence the standard molecular biology procedures required to extract, process, and ultimately visualize a DNA profile.
Step 3: Detailed Explanation:
The correct standard sequential steps involved in DNA fingerprinting are:
1. Isolation of DNA: The process begins by extracting the DNA from the biological sample's cells. (Step d)
2. Digestion of DNA: The isolated DNA is then cut into smaller, specific fragments using restriction endonucleases. (Step a)
3. Separation of fragments: These digested fragments are separated according to their size using gel electrophoresis. (Step e)
4. Blotting: The separated double-stranded fragments are denatured into single strands and transferred (Southern blotted) onto a synthetic membrane like nitrocellulose or nylon. (Step c)
5. Hybridization: (Not listed as an option here, but occurs at this stage using radioactive VNTR probes).
6. Autoradiography: The membrane is exposed to X-ray film. The radioactive probes leave marks on the film, creating the visual "fingerprint" pattern. (Step b)
Thus, the correct chronological order is d $\rightarrow$ a $\rightarrow$ e $\rightarrow$ c $\rightarrow$ b.
Step 4: Final Answer:
The correct sequence is (d), (a), (e), (c), (b).