Expression profiling technologies: A DNA microarray differs from a single-gene promoter/operon fusion in which key ways?

Introduction / Context:
Microarrays and gene fusions both measure gene expression but at different scales and by different principles. Understanding their distinctions helps in choosing appropriate experimental designs for global profiling versus targeted promoter studies.

Given Data / Assumptions:

• Microarrays contain many probes representing many genes.
• Reporter fusions track one promoter–reporter construct per design.
• Microarrays quantify hybridization of labeled cDNA to probes, reflecting mRNA levels.

Concept / Approach:

A gene fusion reports the activity of a single promoter or coding sequence using a measurable reporter. A microarray simultaneously monitors thousands of genes by hybridizing labeled sample cDNA to complementary oligonucleotides affixed on a solid surface, producing intensity-based readouts proportional to transcript abundance.

Step-by-Step Solution:

Verification / Alternative check:

Standard microarray workflows (two-color or single-color) convert mRNA to labeled cDNA and hybridize to preprinted probes, aligning with the listed differences.

Why Other Options Are Wrong:

Any single item alone is incomplete; microarrays differ on all three counts.

Common Pitfalls:

Assuming microarrays measure promoter activity directly; they measure steady-state transcript levels influenced by transcription and mRNA stability.

Final Answer:

All of the above