Gene Control (OCR A Level Biology): Revision Note

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