Practice question

Expressed Sequence Tags are short sequences derived from cDNA clones representing expressed genes. The 5' EST contains coding portion and is relatively conserved across species because protein-coding constraints limit divergence, making it useful for ortholog identification and comparative genomics. The 3' EST corresponds more to 3' UTR, less conserved and more species-specific. SNPs represent single-base variations and VNTRs are tandem repeat copy-number variants, neither inherently coding nor necessarily conserved. Hence 5' ESTs provide cross-species coding information and functional annotation potential.