RNA Sequencing

RNA Sequencing (RNA-seq) is a high-throughput sequencing technology that captures a comprehensive snapshot of the transcriptome, enabling genome-wide quantification of gene expression ¹.

How It Works

RNA-seq begins with extraction of total RNA, followed by optional enrichment of mRNA via poly-A selection or ribosomal RNA depletion. The RNA is fragmented and reverse-transcribed into cDNA, which is ligated with sequencing adapters to create a library. This library is sequenced on platforms such as Illumina, generating millions of short reads.

Reads are aligned to a reference genome or transcriptome, and the number of reads mapping to each gene serves as a proxy for expression level. Unlike microarrays, RNA-seq provides an unbiased view of the transcriptome without requiring predefined probes, enabling detection of novel transcripts, splice variants, and non-coding RNAs.

In synthetic biology, RNA-seq reveals how engineered constructs affect host gene expression, identifies metabolic bottlenecks, and characterizes regulatory circuit behavior at the transcriptome level. Time-course RNA-seq experiments capture dynamic transcriptional responses to circuit induction.

Computational Considerations

RNA-seq analysis requires multi-step bioinformatics pipelines. Read quality control (FastQC, Trimmomatic), alignment (STAR, HISAT2), and quantification (featureCounts, Salmon) precede statistical analysis. DESeq2 and edgeR model count data using negative binomial distributions to identify differentially expressed genes with appropriate multiple-testing correction ². Pathway enrichment analysis tools contextualize expression changes within biological networks.

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