Mutation [Neurosurgery Wiki]

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====== Mutation ======

A **mutation** is a permanent alteration in the **DNA sequence** of a gene, chromosome, or genome. Mutations can affect a single nucleotide or involve large segments of DNA, and they are fundamental drivers of genetic diversity, evolution, and many diseases, including cancer.

===== 🧬 Types of Mutations =====
  * **Point mutation** – A change in a single nucleotide.
    * *Missense*: Changes the amino acid.
    * *Nonsense*: Introduces a premature stop codon.
    * *Silent*: Does not change the amino acid.
  * **Frameshift mutation** – Insertion or deletion (indel) of nucleotides that disrupts the reading frame.
  * **Splice-site mutation** – Alters the normal splicing of exons and introns.
  * **Insertion/Deletion (indel)** – Addition or loss of nucleotides.
  * **Copy number variation (CNV)** – Duplication or deletion of gene regions.
  * **Chromosomal rearrangement** – Inversions, translocations, or duplications of chromosomal segments.

===== 🧠 Functional Consequences =====
  * **Loss of function** – Common in tumor suppressor genes (e.g., *TP53*, *NF2*).
  * **Gain of function** – Leads to new or increased activity (e.g., *EGFR* mutations).
  * **Dominant-negative** – Mutated protein interferes with the normal version.
  * **Neutral** – No significant impact on protein function.

===== 🔬 Detection Methods =====
  * **Sanger sequencing**
  * **Next-Generation Sequencing (NGS)**
  * **qPCR or digital PCR**
  * **FISH (for large rearrangements)**

===== 🧷 Related Concepts =====
  * [[gene]]
  * [[genetic_variation]]
  * [[somatic_mutation]]
  * [[germline_mutation]]
  * [[dna_repair]]