Practice question

Expressed sequence tags derived from cDNA include both 5 prime and 3 prime regions. The 5 prime EST corresponds to coding sequence and highly conserved domains under strong purifying selection, showing lower polymorphism and sequence conservation across species. The 3 prime EST encompasses 3 prime untranslated region, often non-coding, less constrained evolutionarily, accumulating more variations including microsatellite repeats. Therefore, SSR mining in 3 prime EST yields greater polymorphism for marker development. Promoter regions regulate transcription and introns are spliced non-coding sequences outside EST terminology.