Histone genes are clustered but not tandemly repeated in the chicken genome

The recombinant chicken DNA library was screened for histone genes by using pSp17, a recombinant sea urchin DNA probe containing the H2a and H3 genes of Strongylocentrotus purpuratus. Three of the isolated lambda recombinants have been analyzed by restriction enzyme mapping and Southern blotting; one histone H3 gene-encoding recombinant was further analyzed by DNA sequence determination. These studies reveal that the chicken histone genes are not tandemly reiterated, but that, at the least, several histone genes are physically closely linked in a nonrepetitive arrangement within the chicken genome. The evolutionary implications of this arrangement versus that seen in Drosophila and sea urchins is discussed.