Gene Expression and Regulation

This lesson covers how gene expression is controlled in both prokaryotes and eukaryotes, as required by the Edexcel A-Level Biology specification (9BI0, Topic 7). Understanding gene regulation explains how cells with identical DNA can have different structures and functions.

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Why Is Gene Regulation Necessary?

Every cell in a multicellular organism contains the same DNA (the same genome). However, a liver cell looks and functions very differently from a neuron or a muscle cell. This is because different genes are expressed (switched on) in different cell types — a process called differential gene expression.

Gene regulation ensures that:

• Proteins are produced only when and where they are needed
• Resources (energy and raw materials) are not wasted making unnecessary proteins
• Cells can respond to changes in their environment
• Cells differentiate into specialised types during development

Exam Tip: The key principle is that all cells in an organism have the same genome but express different genes. Differentiation is the result of differential gene expression, not differences in DNA content.

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Levels of Gene Regulation

Gene expression can be regulated at multiple levels: