Epigenetic inheritance through heritable changes to gene expression
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Question
Define a mutation.
Answer
A **permanent change to the DNA base sequence**. It is heritable, **not normally reversible**, and can change the **structure** of the protein.
Question
Define an epigenetic change.
Answer
A change in **gene expression** (via methylation / histone tags) **without altering the base sequence**. It is **reversible** and changes the **amount** of protein made.
Question
Mutation vs epigenetic change — the one-question test?
Answer
Did the **DNA base sequence change**? **Yes = mutation**; **no (but expression changed) = epigenetic change**.
Question
Which is reversible — a mutation or an epigenetic change?
Answer
An **epigenetic change** is reversible (a tag can be added/removed); a **mutation** is not normally reversible.
Question
How does each affect the protein?
Answer
A **mutation** can change the protein's **structure**; an **epigenetic change** changes the **amount** of (normal) protein made.
Question
How is gene expression measured?
Answer
By the **amount of mRNA (or protein)** a gene produces. **More mRNA = more highly expressed**; near-zero mRNA = the gene is switched off.
Question
Same gene, different mRNA amounts in two cell types — what does it mean?
Answer
The cells differ in **expression**, not in their DNA — the same gene is read more strongly in one cell (often an epigenetic difference).
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Topic 4.5 hub
Gene expression
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