Which process involves the copying of a DNA sequence into mRNA?

The process that involves copying a DNA sequence into messenger RNA (mRNA) is transcription. During transcription, the DNA double helix unwinds and one of the strands serves as a template for synthesizing a complementary RNA strand. This RNA strand is synthesized using ribonucleoside triphosphates, where adenine pairs with uracil (instead of thymine, which is present in DNA) and cytosine pairs with guanine. The resulting mRNA strand carries the genetic information from the DNA, which can then be translated into a protein by ribosomes.

In contrast, translation refers to the process where the mRNA is decoded by ribosomes to synthesize a polypeptide or protein, and replication is the process of duplicating the entire DNA molecule to ensure that each new cell has the same genetic material. Synthesis is a broader term that can apply to various biological processes, including DNA and protein synthesis, but does not specifically refer to the transcription of DNA into mRNA.