1. RNA POLYMERASE - Transcription is performed by enzymes called RNA polymerases, which link nucleotides to form an RNA strand (using a DNA strand as a template).
2. Stages of transcription
2.1. Initiation. RNA polymerase binds to a sequence of DNA called the promoter, found near the beginning of a gene.
2.2. Elongation. One strand of DNA, the template strand, acts as a template for RNA polymerase. As it "reads" this template one base at a time, the polymerase builds an RNA molecule out of complementary nucleotides, making a chain that grows from 5' to 3'.
2.3. Termination. Sequences called terminators signal that the RNA transcript is complete. Once they are transcribed, they cause the transcript to be released from the RNA polymerase.
3. Not all genes are transcribed all the time. Instead, transcription is controlled individually for each gene (or, in bacteria, for small groups of genes that are transcribed together). Cells carefully regulate transcription, transcribing just the genes whose products are needed at a particular moment.
4. Gene
5. Transcription - is the first step in gene expression. It involves copying a gene's DNA sequence to make an RNA molecule.
