Silent substitution rates in plant and mammalian mtDNAs differ by one or two orders of magnitude, whereas the rates in nDNAs may be similar. Transversions are interchanges of purine for pyrimidine bases, which therefore involve exchange of one-ring and two-ring structures. silent substitution rate in mtDNA is less than one-third that in cpDNA, which in turn evolves only half as fast as plant nDNA. Mitochondrial DNA Mutation Rates David A. Plaisted . You are confusing the mutation/substitution rate in the population, which is used for molecular clocks and other things, and the individual mutation rate. Recently an attempt was made to estimate the age of the human race using mitochondrial DNA. Sanjuán instead investigated the HIV mutation rate in the wild—that is, in blood samples donated by 11 people before they underwent HIV treatment. Substitution A substitution is a mutation that exchanges one base for another (i.e., a change in a single "chemical letter" such as switching an A to a G). As the original poster noted, when a base substitution mutation does not change the amino acid inserted into the gene, it is called a “silent mutation.” When the base substitution does change the amino acid, this is called a “missense mutation.” When the substitution results in a stop codon being inserted, this is called a “nonsense mutation.” I remember this by thinking that “nonsense” is similar to … If the molecular mutation rate, is say, 1/20 (as you assume in your model) then you are expecting a fixation rate per mutation of 1, essentially. The slower rate in mtDNA than in cpDNA is probably due to a lower mutation rate. DNA substitution mutations are of two types. However, that rate was determined with virus growing in the lab. Transitions are interchanges of two-ring purines (A G) or of one-ring pyrimidines (C T): they therefore involve bases of similar shape. Because the pathogen mutates constantly, a single untreated person … As with mitochondrial DNA mutation rates, the mutation rates of nuclear DNA have often been calculated based on evolutionary scenarios rather than on direct methods. HIV, in particular, is known for its astronomical mutation rate, an estimated 3 x 10-5 errors per base, per infection cycle. By measuring the difference in mitochondrial DNA among many individuals, the age of the common maternal ancestor of humanity was estimated at about 200,000 years. This material is inherited always from mother to children only. Eventually, every position has a probability to be a SNP, even if really really tiny probability, depending on the mutation rate, the size of the population, and the time that has past. Such a substitution could: change a codon to one that encodes a different amino acid and cause a small change in the protein produced. By such methods, the average mutation rate for eukaryotes in general was, until fairly recently (see further discussion below), estimated to be about 2.2 x 10 -9 mutations per base pair per year.