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

Step 1: Note the two requirements in the stem. The technique must detect both variation in DNA sequence and gene expression. A single method covering both is asked for.
Step 2: Review what each blot detects. Southern blot detects DNA, so it can show sequence variation but not expression. Northern blot detects RNA, so it reports gene expression but not DNA sequence variation directly. Western blot detects proteins and tells nothing about sequence or transcript levels in a genomic sense.
Step 3: Microarray uses thousands of immobilized probe spots on a chip. DNA microarrays (oligonucleotide arrays, SNP arrays, comparative genomic hybridization arrays) detect sequence variation, copy number changes and single nucleotide polymorphisms. Expression microarrays hybridize labeled cDNA or cRNA to measure mRNA levels for thousands of genes at once, giving gene expression profiles.
Step 4: Because microarray platforms span both DNA sequence variation and gene expression in a single high-throughput format, while each blot is limited to one molecule type, the answer is microarray (option D).