Final Answer:
Cells can amplify the number of copies of a protein made from a single gene at the transcription step. The correct option is A.
Step-by-step explanation:
The process of gene expression involves two main steps: transcription and translation. Transcription occurs in the nucleus, where the DNA sequence of a gene is transcribed into a complementary RNA molecule (mRNA). This mRNA serves as the template for protein synthesis during translation.
Amplification of the number of protein copies is primarily achieved during transcription. Multiple mRNA copies can be transcribed from a single gene, allowing for the potential production of numerous protein molecules. Once transcribed, each mRNA can undergo translation in the cytoplasm to synthesize multiple copies of the corresponding protein.
Option A is the answer.