Which technique measures the expression levels of thousands of genes simultaneously?

Which technique measures the expression levels of thousands of genes simultaneously?

• A. RNA-Seq
• B. qPCR
• C. Mass spectrometry
• D. Western blot

Answer: (A)

Measuring expression levels across thousands of genes requires a genome-wide, quantitative approach. RNA sequencing, or RNA-Seq, does this by converting RNA into cDNA and sequencing it. The number of reads that align to each gene reflects its expression level, and with proper normalization you can compare expression across the whole transcriptome. This provides an unbiased, scalable profile of thousands of transcripts in a single experiment and can reveal novel transcripts and splice variants. In contrast, qPCR is highly targeted, measuring a small set of known genes with gene-specific primers, which isn’t practical for genome-wide profiling. Mass spectrometry and Western blot analyze proteins rather than RNA, so they tell you about protein abundance, not messenger RNA levels, and typically cover fewer targets at a time.

Measuring expression levels across thousands of genes requires a genome-wide, quantitative approach. RNA sequencing, or RNA-Seq, does this by converting RNA into cDNA and sequencing it. The number of reads that align to each gene reflects its expression level, and with proper normalization you can compare expression across the whole transcriptome. This provides an unbiased, scalable profile of thousands of transcripts in a single experiment and can reveal novel transcripts and splice variants.

In contrast, qPCR is highly targeted, measuring a small set of known genes with gene-specific primers, which isn’t practical for genome-wide profiling. Mass spectrometry and Western blot analyze proteins rather than RNA, so they tell you about protein abundance, not messenger RNA levels, and typically cover fewer targets at a time.