Since the 1 920s, when researchers began to study chromosomes, the analysis of human chromosomes has presented a particularly tough technological challenge, simply because there are so many of them.

Pt. A. Gene cloning -- cDNA cloning method using stable expression in mammalian cells / Toru Miki and Stuart A. Aaronson -- Normalization and selection with short-fragment cDNAs / Satish Parimoo, ...