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Small-scale mutations. 1  Point mutation â a change in one base in the DNA sequence. 2  Substitution â when one or more bases in the sequence is replaced by the same number of bases (for example, a cytosine substituted for an adenine).3  Inversion â when a segment of a chromosome is reversed end to end.arge-scale mutations. 1  Copy number variation (CNV) is a type of mutation where large chunks of DNA are inserted, repeated or lost. 2  These regions of DNA can be between 10,000 and 5,000,000 bases long. 3  Duplication of genes. 4  When there is an increase in the number of copies of a gene.
However, these mistakes are rare, and the cell has repair mechanisms that can repair some damage. - Sometimes a permanent change occurs in a cell's DNA and this is called a mutation. - Because a mutation in a gene causes a change in the protein that is made, the enzyme is nonfunctional. Types of mutations - Mutations can range from changes in a single base pair in the coding sequence of DNA to the deletions of large pieces of chromosomes. - Point mutations involve a chemical change in just one base pair and can be enough to cause a genetic disorder. - A point mutation in which one base is exchanged for another is called a substitution. - Most substitutions are missense mutations, where the DNA code is altered so that it codes for the wrong amino acid. - Other substitutions, called nonsense mutations, change the codon for an amino acid to a stop codon. Nonsense mutations cause translation to terminate early. Nearly all nonsense mutations lead to proteins that cannot function normally. - Another type of mutation that can occur involves the gain or loss of a nucleotide in the DNA sequence.