Practice question

Somatic cell hybridization fuses human cells with rodent cells usually mouse creating heterokaryons containing both genomes that subsequently lose human chromosomes randomly during mitotic divisions while retaining mouse complement stably. Clones retaining different sets of human chromosomes screened for human-specific enzyme activity or DNA marker presence allow assignment of gene to particular chromosome via concordance analysis. Panel of hybrids with overlapping retention patterns refines regional localisation pioneering human gene mapping before recombinant DNA techniques enabling first physical assignments of many loci.