Question

Passage:
In the late 1940s, cytogeneticist Barbara McClintock conducted extensive breeding experiments on the inheritance of kernel coloration in maize (Zea mays), challenging the prevailing dogma that genomic architecture remained rigidly static across generations. McClintock focused her microscopic investigations on the ninth chromosome of maize, where she identified a specific chromosomal site prone to frequent breakage during cell division. She designated this breakage locus Dissociation (Ds). Crucially, McClintock observed that Ds was incapable of moving or inducing chromosomal breakage autonomously; its transposition and physical cleavage required the presence of a second, independent genetic factor situated elsewhere in the genome, which she termed Activator (Ac). When Ac was absent from the cell, the Ds locus remained completely inert and fixed at its standard chromosomal position.

McClintock further revealed that the interaction between these two elements directly regulated the phenotypic expression of the C locus, a gene responsible for producing purple anthocyanin pigmentation in the outer aleurone layer of the maize endosperm. In typical wild-type kernels, uninhibited transcription at the C locus generates uniform purple pigmentation. However, when an activated Ds element transposes and inserts itself directly into the C gene sequence, it disrupts the coding region, entirely arresting anthocyanin synthesis and producing colorless, yellow kernels. If Ac subsequently stimulates Ds to excise itself from the C locus during subsequent endosperm cell divisions, functional pigment production is restored in descendant cell lineages, yielding a distinctive variegated or mosaic pattern of purple sectors on a colorless background.

Beyond characterizing the structural breakage caused by Ds, McClintock documented that the timing and frequency of transposition events depended strictly on the dosage of Ac elements within the nucleus. Counterintuitively, higher numbers of Ac copies delayed transposition until later stages of developmental differentiation, resulting in smaller, more numerous variegated patches rather than large pigmented sectors. Although McClintock presented her comprehensive findings at the 1951 Cold Spring Harbor Symposium, the scientific community largely met her discovery of mobile genetic elements with skepticism, as contemporary geneticists remained wedded to the conceptualization of chromosomes as unalterable linear arrays of fixed genes.

Based on the explicit details provided in the passage, match each genetic element or nuclear condition on the left with its corresponding functional characteristic or effect on the right.