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Point Mutations.

1. Substitution -one base is incorrectly added during replication and replaces the pair in the corresponding position on the complementary strand. . This mutation is linked to sickle-cell anemia.
2. Insertion - one or more extra nucleotides are inserted into replicating DNA, often resulting in a frameshift. . Linked to one form of beta-thalassemia.
3. Deletion - one or more nucleotides is 'skipped' during replication or otherwise excised, often resulting in changes. . Linked to Cystic fibrosis.

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Chromosomal Mutations.

1. Inversion - a region of a chromosome is flipped and reinserted. Linked to Opitz-Kaveggia syndrome.
2. Deletion - a region of a chromosome is lost resulting in the absence of all the genes in that area. Linked to Cri du chat syndrome.
3. Duplication - a region of a chromosome is repeated. This results in an increase in dosage from the genes in that region. Linked to some cancers. 4.Translocations - region from one chromosome is aberrantly attached to another chromosome. Linked to one form of Leukemia.

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Copy Number Variations.

1. Gene Amplification - the number of tandem copies of a locus is increased. i.e some breast cancers.
2. Expanding Trinucleotide Repeat - the normal number of repeated trinucleotide sequence is epanded. Linked to Fragile X syndrome (Huntington's disease)

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