OCR A Level Biology

Revision Notes

6.1.2 Gene Control

Gene Control

  • The nucleus of every cell in the human body contains the same genes
    • However, not every gene is expressed in every cell
    • In addition, not all of these genes are expressed all the time
  • There are several mechanisms that exist within cells to make sure the correct genes are expressed in the correct cell at the correct time
    • These mechanisms are known as regulatory mechanisms
    • They control which genes are expressed at different points in time (e.g. during development)
  • There are three main types of regulatory mechanisms, including:
    • Regulation at the transcriptional level (i.e. regulatory mechanisms that occur during transcription)
    • Regulation at the post-transcriptional level (i.e. regulatory mechanisms that occur after transcription)
    • Regulation at the post-translational level (i.e. regulatory mechanisms that occur after translation)
  • These regulatory mechanisms are controlled by many different regulatory genes

Structural and regulatory genes

  • A structural gene codes for a protein that has a function within a cell (e.g. enzymes, membrane carriers, hormones etc.)
    • For example, the F8 gene codes for the protein Factor VIII involved in blood clotting
  • Regulatory genes code for proteins (or various forms of RNA) that control the expression of structural genes

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