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Mutation rate

MtDNA and its susceptibility to mutation

Structure of mitochondira-chromosome can be seen with the presence of dark spots
MtDNA are replicated independently of each other, they do not undergo recombination. MtDNA replication occurs with a much higher error rate than nuclear DNA, this
increases the risk of mutation[1]. A condition called heteroplasmy occurs with mixtures of two or more sub populations of mitochondrial DNA. Heteroplasmy results from the mutation of mtDNA through mitosis, the mutated chromosome spreads, resulting in multiple mtDNA in a sample. The frequency of heteroplasmy is relatively rare with 2-8%[1] of samples indicating a mutation when cross referenced with a relative, mutation can occur through point mutation: insertion or deletion of a nucleic acid, this can cause a frame shift resulting in the misreading of an mRNA strand. Even with the modification of the genome, mtDNA can still be used in identification with only small variations within the genome insufficient to misidentify a person.
Some mutations of mitochondia can result in a number of diseases, these conditions mainly affect the energy capacity of cells of a particular tissue to meet the specific energy requirements. The severity of the illness is dependent on the proportion of the affected mitochondria.
mitochondrial genome

[1]Holland, M.M., Parsons, T.J., 1999, 'Mitochondrial DNA sequence analysis-validation and use for forensic casework',
mitochondrial genome:http://images.google.com.au
mitochondrial Genome: Wikipedia, http://commons.wikimedia.org/wiki/File:Mitochondrial_DNA_en.svg
mitochondria structure: http://academic.brooklyn.cuny.edu/biology/bio4fv/page/mito.htm