||Caskey CT, Kruh GD. The HPRT locus. Cell. 1979 Jan16(1):1-9. p.6 right column 2nd paragraphPubMed ID369702
||McBride OW, Ozer HL. Transfer of genetic information by purified metaphase chromosomes. Proc Natl Acad Sci U S A. 1973 Apr70(4):1258-62.PubMed ID4515624
||Primary source abstract: "Metaphase chromosomes isolated from Chinese hamster fibroblasts were incubated with mouse A(9) cells containing a mutation at the hypoxanthine-guanine phosphoribosyl transferase (hprt) locus. Cells were plated in a selective medium, resulting in death of all unaltered parental A(9) cells."
||P.6 right column 2nd paragraph to 3rd paragraph: "Gene Transfer: The successful use of metaphase chromosome preparations from human cells to transfer the human HPRT gene to mouse HPRT- cells was initially reported by McBride and Ozer (primary source). While the transfer frequency was low (10^-7), numerous laboratories have confirmed the observation (Willecke and Ruddle, 1975 Wullems, Van der Horst and Bootsma, 1975 Degnen et al., 1976). Two new technical modifications in the transfer methods have improved the frequency of transfer, making the technique extremely valuable. The entrapment of chromosomes in phospholipid vesicles enhanced HPRT gene transfer to a frequency of 10^-5-10^-6 (Mukherjee et al., 1978). Using a technique also used with viral DNA transfection (Stow and Wilkie, 1976), Miller and Ruddle (1978) found that DMSO (Dimethyl sulfoxide) increased the frequency of transfer of the HPRT gene 4×10^-5." HGPRT=Hypoxanthine-guanine phosphoribosyltransferase