Final answer:
In eukaryotic cells, the variety of cellular structures and functions is attributed to RNA processing, a step in gene expression regulation unique to eukaryotes.
Step-by-step explanation:
The general genetic process believed to account for the variety of cellular structures and functions in eukaryotic cells is RNA processing. This includes the modification of RNA after it is transcribed, such as splicing out introns and joining exons. Eukaryotic cells are complex, and their ability to express different genes through RNA processing allows for the differentiation into various cell types with distinct structures and functions. This is unlike prokaryotic cells, which mainly regulate gene expression by controlling the amount of transcription, due to their simpler organization.