Which term best describes genes that are not required for survival but can enhance an organism's fitness?

The term that best describes genes that are not required for survival but can enhance an organism's fitness is "non-essential genes." These genes often contribute to traits that improve an individual's ability to reproduce or adapt to its environment, which can be considered as enhancing their overall fitness. While they are not critical for basic survival, their presence may provide advantages that allow organisms to thrive in particular conditions or to compete more effectively for resources, mates, or other factors important for reproduction.

In contrast, essential genes are crucial for basic life processes and are needed for survival. Decorative genes, although they might suggest a link to traits that are visually appealing or seem to serve an aesthetic purpose, are not a standard term used in genetics and may not properly convey their role in fitness enhancement. Dominant genes refer to a specific pattern of inheritance where one allele masks the effect of another in heterozygous individuals, which does not directly relate to whether a gene is essential or non-essential for survival or fitness enhancement. Thus, non-essential genes accurately represent the concept of providing beneficial traits without being critical for survival.