What is transcription?

• A. Process of copying a nucleotide sequence of DNA to form a complementary strand of mRNA
• B. The translation of mRNA into a polypeptide
• C. The replication of DNA
• D. The degradation of RNA in the nucleus

Answer: (A)

Transcription is the process of copying a DNA sequence into an RNA molecule. An RNA polymerase enzyme binds to a promoter on the DNA, unwinds a small region, and then synthesizes an RNA strand that is complementary to the DNA template, adding ribonucleotides in the 5' to 3' direction. The resulting transcript is an RNA version of the gene and, in cells like ours, often becomes mature mRNA after processing before it can be used to make protein.

This is different from translation, which uses the mRNA to assemble a polypeptide; from replication, which copies DNA to make another DNA molecule; and from RNA degradation, which breaks RNA down rather than building it.