How does transcription function in gene expression?

Transcription is the process of making an RNA copy of a gene's DNA sequence.

During transcription, the DNA double helix is unwound and one of the strands is used as a template to make a complementary RNA molecule. The RNA polymerase enzyme reads the DNA sequence and adds nucleotides to the growing RNA strand according to the base pairing rules (A-U and C-G). This process continues until the RNA polymerase reaches a stop signal and the RNA molecule is complete.

The RNA molecule produced during transcription is called messenger RNA (mRNA) because it carries the genetic information from the DNA to the ribosomes, where it is translated into a protein. Before leaving the nucleus, the mRNA undergoes post-transcriptional modifications, such as splicing and capping, which help to protect and regulate the mRNA.

Transcription is a critical step in gene expression because it allows the genetic information encoded in the DNA to be translated into functional proteins. The rate of transcription can be regulated by various factors, such as transcription factors and epigenetic modifications, which can affect the accessibility of the DNA to the RNA polymerase enzyme. Dysregulation of transcription can lead to various diseases, including cancer.