Genetic Mutations Occur in any organism, from people and other animals to plants, bacteria, fungi, and protists. A mutation is any change in the nucleotide sequence of an organism's DNA. Some mutations are more drastic than others.

Genetic Mutations Mutations can be caused by external (exogenous) endogenous (native) factors errors in the cellular machinery Physical or chemical agents that induce mutations in DNA are called mutagens and are said to be mutagenic. Exogenous factors: environmental factors such as sunlight, radiation, and smoking can cause mutations. Endogenous factors: errors during DNA replication can lead to genetic changes as can toxic by-products of cellular metabolism.

Genetic Mutations The DNA sequence of a gene can be altered (changed) in a number of ways. Gene mutations have varying effects on health, depending on where they occur and whether they alter the function of essential proteins. The types of mutations include: missense nonsense insertion deletion frameshift duplication repeat expansion.

Genetic Mutations

Small-scale mutations Point mutation – a change in one base in the DNA sequence. Substitution – when one or more bases in the sequence is replaced by the same number of bases (for example, a cytosine substituted for an adenine).

Genetic Mutations Missense- a change of a base pair that results in the substitution of one amino acid for another. Nonsense Mutation- a change of a base pair that results in the substitution of one amino acid that now results in a STOP signal. This ends the protein too early making it function improperly or not at all.

Genetic Mutations Insertion – when a base is added to the sequence.

Genetic Mutations Deletion – when a base is deleted from the sequence.

Genetic Mutations Frameshift mutation: This type of mutation occurs when the addition or loss of DNA bases changes a gene’s reading frame. A reading frame consists of groups of 3 bases that each code for one amino acid. A frameshift mutation shifts the grouping of these bases and changes the code for amino acids. The resulting protein is usually nonfunctional. Insertions, deletions, and duplications can all be frameshift mutations.

Genetic Mutations Inversion – when a segment of a chromosome is reversed end to end.

Large-scale mutations Copy number variation (CNV) is a type of mutation where large chunks of DNA are inserted, repeated or lost. These regions of DNA can be between 10,000 and 5,000,000 bases long. Duplication of genes. When there is an increase in the number of copies of a gene. Deletions of large regions of the chromosome. Loss of one copy of a gene in an organism that previously had two copies. Loss of both copies of the same gene. Movement of sections of DNA from one location to another. Addition of an extra copy of a chromosome. For example, an extra copy/partial copy of chromosome 21 results in Down’s syndrome. Genetic Mutations