The native Orc6 promoter and UAS regulatory sequences are fused upstream of a C-terminally truncated form of Orc6, which is tagged at the N-terminal end with GFP.

Orc6^{ΔC.220.Orc6.UAS.GFP} fails to rescue Orc6³⁵

Expression of Orc6^{ΔC.220.T:Avic\GFP} results in the release of Orc6³⁵ mutant cells from G1 arrest, as shown by the ratio of cells containing either 1 or 2 centrosomes being indistinguishable from cells obtained from heterozygous siblings.

Chromosomes from neuroblasts isolated from Orc6³⁵ mutants carrying Orc6^{ΔC.220.T:Avic\GFP} are able to incorporate BrdU, and therefore are able to replicate DNA. Brains observed in these larvae are significantly reduced in size compared with heterozygous or wild-type larval brains, suggesting severe defects in cell proliferation and larval brain development.

Orc6³⁵ mutant neuroblasts carrying Orc6^{ΔC.220.T:Avic\GFP} accumulate at mitosis. The number of mitotic neuroblasts derived from these transgenic flies increases approximately 4-fold compared with Orc6³⁵ mutant cells.

A large number of metaphase-like figures are observed in Orc6³⁵ mutant cells expressing Orc6^{ΔC.220.T:Avic\GFP}. Cells in other stages are also found (e.g. anaphase-like figures are found, containing broken chromosomes), some polyploid with multiple centrosomes, while others exhibit multiple centrosomes but don't have any DNA present.