RNA–DNA differences (RDDs) challenge the traditional view of RNA as a faithful copy of DNA, arising through RNA editing, transcriptional errors, and oxidative damage. Reactive oxygen species (ROS) play a central role, inducing lesions like 8-oxo-guanine that compromise transcription and translation, leading to dysfunctional proteins. This review explores the biochemical basis of RDDs, their exacerbation under oxidative stress, and their dual roles in cellular adaptation and disease. RDDs contribute to genomic instability and are implicated in cancers, neurodegenerative disorders, and autoimmune diseases, while also driving phenotypic diversity. Drawing on terrestrial and spaceflight studies, we highlight the intersection of oxidative stress, RDD formation, and cellular dysfunction, proposing innovative mitigation approaches. Advancements in RDD detection and quantification, along with ROS management therapies, offer new avenues to restore cellular homeostasis and promote resilience. By positioning RDDs as a hallmark of genomic entropy, this review underscores the limits of biological adaptation. Furthermore, the prevalence of guanine-rich codons in antioxidant genes increases their susceptibility to ROS-induced oxidative lesions, linking redox stress, genomic instability, and constrained adaptation. These insights have profound implications for understanding aging, disease progression, and adaptive mechanisms in both terrestrial and space environments.

RNA-DNA differences (RDDs) challenge the traditional view of RNA as a faithful copy of DNA, arising through RNA editing, transcriptional errors, and oxidative damage. Reactive oxygen species (ROS) play a central role, inducing lesions like 8-oxo-guanine that compromise transcription and translation, leading to dysfunctional proteins. This review explores the biochemical basis of RDDs, their exacerbation under oxidative stress, and their dual roles in cellular adaptation and disease. RDDs contribute to genomic instability and are implicated in cancers, neurodegenerative disorders, and autoimmune diseases, while also driving phenotypic diversity. Drawing on terrestrial and spaceflight studies, we highlight the intersection of oxidative stress, RDD formation, and cellular dysfunction, proposing innovative mitigation approaches. Advancements in RDD detection and quantification, along with ROS management therapies, offer new avenues to restore cellular homeostasis and promote resilience. By positioning RDDs as a hallmark of genomic entropy, this review underscores the limits of biological adaptation. Furthermore, the prevalence of guanine-rich codons in antioxidant genes reflects a compensatory strategy against ROS-induced damage, linking redox stress, genomic instability, and constrained adaptation. These insights have profound implications for understanding aging, disease progression, and adaptive mechanisms in both terrestrial and space environments.

The yeast metabolic cycle (YMC) in Saccharomyces cerevisiae provides a tractable model for examining how mitochondrial respiration, redox timing, and metabolic phase shape transcriptome abundance and fidelity. Ribosomal-RNA-depleted whole-transcriptome RNA sequencing (WRS) and RNA-seq-derived mismatch analyses were performed across low-dissolved-oxygen (Low-DO)/high-respiration and high-dissolved-oxygen (High-DO)/lower-respiration phases. Among 1505 phase-differentially expressed genes, Low DO was enriched for ribosome biogenesis, rRNA processing, translation, sulfur metabolism, and protein synthesis, whereas High DO was enriched for oxidant detoxification, oxidoreductase activity, and redox-buffering-related pathways. Generalized linear mixed models identified a substitution-class-dependent Low-DO-associated RNA-seq mismatch response. The strongest mismatch-level increase occurred in the collapsed C > T/G > A-compatible class, whereas C > A/G > T did not increase. This pattern was not consistent with a simple single-lesion model and instead supported a mixed Low-DO-associated RNA-seq sequence-discordance landscape. Variant-rate modeling additionally detected T > C/A > G and T > A/A > T increases, indicating that multiple biological and technical processes may contribute to the observed spectrum. Recurrence analysis showed that most called variants were sample-specific, supporting a transient RNA-seq mismatch landscape rather than stable DNA mutation. These findings establish the YMC as a reductionist eukaryotic framework for studying how metabolic phase and redox state shape transcriptome fidelity.