Abstract
We have successfully used a DNA.cDNA molecular hybridization assay to directly determine the presence or absence of human beta globin gene sequences in 20 human-mouse somatic cell hybrids, each of which contained a different subset of human chromosomes. The assay is specific for the individual human globin genes and will detect the presence of a globin gene if the relevant chromosome is present in only 10% of the cells of a hybrid population. The content of human chromosomes in each hybrid clone was characterized by Giemsa 11 staining, Giemsa trypsin-Hoechst 33258 staining, and by the use of 22 independent isozyme markers for 17 different human chromosomes. All human chromosomes were present in one or more cell lines devoid of the human beta globin gene except for 6, 8, 9, 11, and 13. Among these latter chromosomes, only chromosome 11 was present in the six hybrid clones that contained the human beta globin gene. In fact, chromosome 11 was the only human chromosome that was present in all of the six hybrid clones found to be positive for the human beta globin gene. Two sister clones, 157-BNPT-1 and 157-BNPT-4, had similar subsets of human chromosomes except that 11 was present only in 157-BNPT-4. 157-BNPT-4 contained the human beta globin gene while 157-BNPT-1 did not. DNA from three hybrid lines was also annealed to purified human gamma globin cDNA; two lines positive for human beta globin gene sequences also contained human gamma globin gene sequences while one line was negative for both beta and gamma gene sequences. On the basis of these results, the human beta and gamma globin genes have been assigned to human chromosome 11.