Chromosome Mutations and Aneuploidy

This lesson covers mutations that affect entire chromosomes or large sections of chromosomes, including changes in chromosome number (aneuploidy and polyploidy) and structural rearrangements. These topics are required by the Edexcel A-Level Biology specification (9BI0, Topic 8).

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Types of Chromosome Mutation

Chromosome mutations are large-scale changes that affect the structure or number of chromosomes. They are distinct from gene mutations, which affect individual bases.

Structural Chromosome Mutations

Type	Description	Consequence
Deletion	A section of a chromosome is lost	Loss of genes; often lethal or causes severe abnormalities
Duplication	A section is copied, producing an extra copy	May lead to gene dosage effects; important in evolution
Inversion	A section is reversed (flipped 180°)	Genes may be disrupted at breakpoints; can suppress recombination
Translocation	A section is transferred to a non-homologous chromosome	May disrupt genes at breakpoints; can cause problems during meiosis

Reciprocal Translocation