What is the primary difference between orthologous and paralogous genes?

• A. Paralogous genes are the result of speciation events, while orthologous genes are the result of gene duplication events.
• B. Orthologous genes are non-homologous, while paralogous genes are homologous.
• C. Orthologous genes and paralogous genes both result from gene duplication.
• D. Orthologous genes are the result of speciation events, while paralogous genes are the result of gene duplication events.

Answer: (D)