Biological regulation is inherently recursive. Genes give rise to proteins that circle back to shape transcription, stress responses activate programs that later dampen the same response, and chromosomal dosage changes ripple through development until they settle into recognizable disease states. This paper repositions Reflexive Category Theory (RCT) as a biology-centered descriptive framework for that kind of recurrent causality. Rather than presenting RCT as a mathematical structure applied from the outside, we treat it as a disciplined way to represent how molecular systems repeatedly act on the conditions that produced them. The concept is developed through three disease-relevant settings: the p53-MDM2-BRCA1 damage-response network, the MYC-TERT telomerase reactivation axis, and the dosage-rewired hematopoietic landscape of trisomy 21. Across these examples, the central claim is that reflexive modeling is valuable not because it replaces experiment, but because it preserves mechanistic continuity across multi-step, feedback-rich biology. In that sense, RCT is proposed here as a conceptual bridge between molecular evidence and system-level interpretation in oncology and genetic disease.