Genetic Mutation

Mutation Greatest source of genetic diversity A change in the sequence of nucleotides of a gene. Some changes to the DNA will alter the protein so that it no longer works normally, while other changes may have no effect. Caused by many factors including environmental causes (radiation and mutagenic chemicals) or are sometimes random chance events.

Genetic Mutation

Types of Mutations Point Mutation oA point mutation is a change of a single nucleotide in a sequence from one kind of base to another. Insertion Deletion Substitution

Genetic Mutation Insertion A mutation caused by the insertion of at least one extra nucleotide base in a DNA sequence. THE BIG FAT CAT ATE THE WET RAT Normal THE BIG ZFA TCA TAT ETH EWE TRA Insertion

Genetic Mutation Deletion A mutation caused by the deletion of at least one nucleotide base in a DNA sequence. THE BIG FAT CAT ATE THE WET RAT Normal THB IGF ATC ATA TET HEW ETR AT Deletion

Genetic Mutation Substitution A mutation caused by a nucleotide base being replaced by a different one. THE BIG FAT CAT ATE THE WET RAT Normal THE BIZ FAT CAT ATE THE WET RAT Missense THE BIG RAT Nonsense

Genetic Mutation Frameshift Mutation A type of mutation that results from insertion or deletion of a single base pair into, or from, an open reading frame in the normal DNA sequence. The entire sequence downstream of the mutation is translated into a polypeptide with a garbled amino acid sequence from the mutated codon onwards.

Genetic Mutation Silent Mutation Silent mutations are DNA mutations that do not result in a change to the amino acid sequence of a protein.

Genetic Mutation

Chromosomal Mutation During meiosis, chromosomes pair up and may undergo crossover. Usually, the result is an equal exchange of alleles between homologous chromosomes. Errors in the exchange can cause chromosomal mutations.

Genetic Mutation Chromosomal Mutation A chromosomal deletion occurs when a piece of a chromosome is lost. At the end of meiosis, one of the cells will lack the genes from that missing piece. Such deletions are usually harmful. A chromosomal duplication occurs when a piece remains attached to its homologous chromosome after meiosis. One chromosome will then carry both alleles for each of the genes in that piece.

Genetic Mutation Chromosomal Mutation An chromosomal inversion occurs when a piece reattaches to its original chromosome, but in a reverse direction. A chromosomal translocation occurs when a chromosome piece ends up in a completely different, nonhomologous chromosome. A chromosomal mutation can move an entire gene to a new location. Such a change, called a gene rearrangement, is likely to disrupt the gene’s function in other ways.

Genetic Mutation

Mutation Many genetic changes will cause no change in the appearance or function of organisms. The results of genetic change may be harmful, beneficial, or neutral; most changes are neutral and may not be passed on to offspring. Mutations that occur in gametes can be passed on to offspring, but mutations in body cells affect only the individual in which they occur.

Genetic Mutation Body-cell v. Sex-cell Mutation If a mutation occurs in a somatic (body) cell, the change may be silent or it may change the function of the cell. that genetic change will be lost when the owner of the cell dies. Only a mutation in a gamete may be passed on to the next generation. However, any such mutation may be silent or have little effect. Only rarely do mutations cause dramatic changes in future generations.