Question

Which of the following techniques is used for detection of variation in DNA sequence and gene expression?

• A. Northern blot
• B. Southern blot
• C. Western blot
• D. Microarray

Hint:

Look for the high-throughput chip that reads many genes for both sequence and expression.

Answer 1

The Correct Option is D

This question is really asking which tool is versatile enough to do two jobs at the same time: read changes in the genetic code and read how busy genes are.

The three blotting methods are each single-purpose. The classic memory aid is SNoW DRoP: Southern handles DNA, Northern handles RNA, Western handles protein. So Southern alone could flag a DNA change, and Northern alone could report expression, but neither does both. Western is concerned only with the protein product.

Microarray technology breaks that one-job limit. A chip is printed with vast numbers of known probe sequences. When you hybridize genomic DNA to it, you can pick up single nucleotide polymorphisms, deletions and copy-number shifts, which is sequence variation. When you instead hybridize labeled transcripts (cDNA or cRNA), the signal intensity at each spot reflects how much of that gene's mRNA is present, giving a full expression snapshot across thousands of genes. One platform, two readouts.
\[\boxed{\text{Microarray}}\]