A tandem array containing 4 copies of a histone gene repeat unit. In each repeat a number of synonymous mutations have been introduced into each histone gene (resulting in the addition and removal of restriction enzyme sites) so that the transgenic repeats can be distinguished molecularly from the endogenous copies.

Wild-type His1 gene in the context of a histone gene repeat tandem array. A number of synonymous mutations have been introduced (resulting in the addition and removal of restriction enzyme sites) so that the transgenic gene can be distinguished molecularly from the endogenous gene copies.

Wild-type His2A gene in the context of a histone gene repeat tandem array. A number of synonymous mutations have been introduced (resulting in the addition and removal of restriction enzyme sites) so that the transgenic gene can be distinguished molecularly from the endogenous gene copies.

Wild-type His2B gene in the context of a histone gene repeat tandem array. A number of synonymous mutations have been introduced (resulting in the addition of restriction enzyme sites) so that the transgenic gene can be distinguished molecularly from the endogenous gene copies.

Wild-type His3 gene in the context of a histone gene repeat tandem array. A number of synonymous mutations have been introduced (resulting in the addition and removal of restriction enzyme sites) so that the transgenic gene can be distinguished molecularly from the endogenous gene copies.

Wild-type His4 gene in the context of a histone gene repeat tandem array. A number of synonymous mutations have been introduced (resulting in the addition and removal of restriction enzyme sites) so that the transgenic gene can be distinguished molecularly from the endogenous gene copies.