15.2 - Regulation of Transcription and Translation

What are the general principles in preventing the expression of a gene by preventing transcription?

• For transcription to begin the gene needs to be stimulated by specific molecules that move from the cytoplasm into the nucleus. These molecules are called transcriptional factors. 
• Each transcriptional factor has a site that binds to a specific region of DNA to begin the process of transcription.
• When it binds, it stimulates this region of DNA to begin the process of transcription.
• mRNA is produced and the genetic code it carries is then translated into a polypeptide.
• When a gene is not being expressed, the site on the transcriptional factor that binds to DNA is blocked by an inhibitor molecule.
• This inhibitor molecule prevents the transcriptional factor binding to DNA and so prevents transcription and polypeptide synthesis.

Hormones like oestrogen can switch on a gene and thus start transcription by combining with a receptor on the transcriptional factor…