What occurs during the process of transcription in cells?

During the process of transcription, genetic information is copied from DNA to messenger RNA (mRNA). This process occurs in the nucleus of eukaryotic cells and involves several key steps. First, the DNA double helix unwinds, and one of the strands serves as a template for the synthesis of RNA. RNA polymerase, the enzyme responsible for transcription, binds to a specific region of the DNA called the promoter and adds complementary RNA nucleotides to form the mRNA strand.

This newly synthesized mRNA mirrors the sequence of the DNA template strand but replaces thymine (T) with uracil (U). Once the RNA polymerase reaches a termination signal in the DNA sequence, transcription ends, and the mRNA strand is released. This mRNA then undergoes processing, including splicing and the addition of a 5' cap and poly-A tail, before it is transported out of the nucleus to the ribosomes, where translation into protein takes place.

In essence, transcription is a crucial step in gene expression as it converts the code stored in DNA into a format (mRNA) that can be used to synthesize proteins, determining the traits and functions of the cell.