Which occurs during transcription? A. DNA is copied to create a second DNA strand. B. mRNA codons and tRNA anticodons assemble amino acids. C. DNA is unzipped with the aid of DNA polymerase. D. mRNA is synthesized from a strand of DNA.

During transcription: D. mRNA is synthesized from a strand of DNA. A gene's protein building instructions are transcribed to messenger RNA (mRNA). mRNA carries the code from DNA to the ribosomes where translation into a protein occurs. Transcription occurs in three stages.