Genetic abberations by scale and effect.

Mutations are said to occur when any amount of a genomic sequence is changed during NA replication or repair. In humans, every individual is estimated to have between 200-300 unique mutations at birth. Most mutations are neutral, meaning they have no effect on the carrier's fitness; fewer are deleterious, with a negative effect, and the fewest are beneficial, meaning they confer a fitness advantage.

Single-point mutations

Also known simply as point mutations, these occur when a single base pair is inserted, deleted, or substituted.

By change

Frameshift mutations: Also known as indel mutations, these occur when base pairs are inserted or deleted. In protein-coding regions, this shifts every codon triplet downstream, and thus the remainder of the amino acid/protein product.

CATACT → CATGACT (insertion)
CATACT → CAACT (deletion)

Substitution mutations: These occur when a base pair is incorrectly replicated, and is replaced by another in the NA product. They are further categorised as translations (A↔T or G↔C) and transversions (pyrimidine-pyrimidine or purine-purine).

CATACT ↔ CATTCT (A-T translation) or CATACT ↔ GATACT(G-C translation)
CATACT ↔ CGTACT (purine transversion) or CATACT ↔ TATACT (pyrimidine transversion)

By effect

Missense mutations: Also known as nonsynonymous mutations, these occur when a point mutation produces a non-synonymous codon with the original and, therefore, a amino acid product.

Nonsense mutations: These occur when a point mutation produces a stop codon (usually UAA, UAG, UGA) which terminates the protein product at that point.

Silent mutations: Also called synonymous mutations, these occur when a point mutation produces a synonymous codon with the original and, therefore, the same amino acid product. As such, these mutations are always essentially selectively neutral.

Large-scale Mutations

Amplification

Polyploidy