Chinese hamster cells with a minichromosome containing the centromere region of human chromosome 1

We describe a series of primary and secondary hamster-human hybrids which have selectively retained a small amount of human DNA. The hybrid XJM12.1.3 contains an estimated 4000-8000 kb of human DNA, and for a secondary hybrid derived from it, XEW8.2.3, our estimate is 1000-2000 kb. The hybridization of Southern blots of DNA from these hybrids with a variety of human satellite DNA probes reveals that these lines include centromere sequences of human chromosome 1. The identifiable human DNA is in the form of a minichromosome, as detected by in situ hybridization in the light microscope and in the electron microscope. At mitosis, the minichromosome can be observed to have kinetochores and to be associated with microtubules. Therefore, it can segregate in a stable fashion. It may be significant that in the selection of the hybrids we had selected for a human gene which has been mapped on human chromosome 1.