Histone genes are located at the sphere loci of newt lampbrush chromosomes.

In situ hybridization experiments on mitotic and lampbrush chromosomes show that histone genes and an associated 222 bp repeated sequence, satellite 1, are located at or near the sphere loci of chromosomes 2 and 6 of the newt Notophthalmus viridescens. During the lampbrush chromosome stage, transcripts of the histone genes and of satellite 1 occur on loops associated with the spheres. Histones genes are located at sites on the mitotic chromosomes of Triturus cristatus and T. alpestris which are consistent with the known positions of spheres on their lampbrush chromosomes.