Different CNV mechanisms, such as aneuploidy and focal amplifications, can have varying fitness costs that shape evolutionary trajectories. Aneuploidy, which involves whole chromosome duplications or deletions, can incur significant fitness costs due to imbalances in gene dosage and disrupted cellular processes. The presence of extra or missing chromosomes can lead to changes in gene expression, protein levels, and cellular functions, resulting in decreased fitness. In contrast, focal amplifications, which involve duplications or deletions of specific genomic regions, may have lower fitness costs as they only affect a subset of genes. Focal amplifications can provide adaptive benefits by increasing the dosage of specific genes that confer a selective advantage without the detrimental effects of aneuploidy.
The fitness costs associated with aneuploidy versus focal amplifications can influence the evolutionary trajectories of populations. Aneuploidy may be less favored in the long term due to its higher fitness costs and potential destabilizing effects on cellular processes. In contrast, focal amplifications that provide adaptive benefits with minimal fitness costs are more likely to be maintained in populations over time. The balance between the fitness costs and benefits of different CNV mechanisms determines their prevalence and persistence in evolving populations, shaping the evolutionary trajectories towards adaptation or extinction.