15.2 - Regulation of Transcription and Translation

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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


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