Practice question

Expressed Sequence Tags represent partial single-pass sequences of complementary DNA clones derived from messenger RNA, capturing actively expressed portion of genome for gene discovery. Cellular mRNA is isolated, reverse transcribed into cDNA, cloned into plasmid vectors, and then randomly sequenced from 5' or 3' ends to generate ESTs. This approach excludes introns and intergenic regions present in genomic DNA. Mitochondrial DNA and STR mapping produce entirely different data types. Thus cDNA libraries constitute primary source material, providing functional gene identification and molecular marker development.