Expression Information

In RNA sequencing (RNA-Seq), gene expression is measured by counting the number of reads that align to each gene, but raw counts need to be normalized for factors like gene length and sequencing depth. RPKM (Reads Per Kilobase of transcript per Million mapped reads) normalizes by adjusting for both gene length and total read count within a sample, making it useful for comparing gene expression within a single sample. TPM (Transcripts Per Million) also accounts for gene length but normalizes after adjusting for gene length, making it better for comparing expression across different samples. For cross-sample comparisons, methods like DESeq2 and EdgeR are preferred, as they use statistical models to correct for sequencing depth and other biases, providing more accurate results for differential gene expression analysis.