Question

Which molecular technique is used to detect specific mRNA molecules in a sample?

• A. Southern Blot
• B. Northern Blot
• C. Western Blot
• D. PCR

Hint:

Southern blot → DNA
Northern blot → RNA (mRNA detection)
Western blot → Protein

Answer 1

The Correct Option is B

This question covers the classic "blotting" techniques in molecular biology. These methods are used to identify a specific molecule of interest (DNA, RNA, or protein) within a complex mixture. They generally involve separating the molecules by size using gel electrophoresis, transferring them to a solid membrane, and then using a labeled probe to detect the target molecule.
Understanding the Question The question asks to identify the specific blotting technique designed for the detection of RNA, particularly messenger RNA (mRNA).
Key Concepts and Approach The key concept is the distinction between the three main types of blotting techniques. A common mnemonic, "SNOW DROP," helps to remember them:
Southern $\rightarrow{}$ DNA
Northern $\rightarrow{}$ RNA
O - O
Western $\rightarrow{}$ Protein
Detailed Solution
Southern Blot: This technique is used to detect specific sequences of DNA. It is named after its inventor, Edwin Southern.
Western Blot: This method uses antibodies as probes to detect specific proteins.
Northern Blot: This technique was developed as an analogy to the Southern blot and is used to detect and quantify specific sequences of RNA, such as mRNA. It is a powerful tool for studying gene expression, as the amount of a specific mRNA in a sample often correlates with the level of activity of that gene.
Conclusion: Based on this distinction, the Northern blot is the correct technique for detecting mRNA.