Mechanisms of directed mutation

Article Abstract:

Three hypotheses were tested to explain the function of selection in the generation of adaptive mutation in Escherichia coli. The first hypothesis postulates that a reverse flow of genetic information from altered proteins to the DNA produces mutation. The second contends that a specific condition calls for the transcription of inactive genes while the third states that repair mechanisms are responsible for mutations. These hypotheses were not able to account for the observed adaptive mutation. A new hypothesis stating that the generation of multiple copies of genes increases the chance for errors and may thus account for adaptive mutations is forwarded.

Causes of, Adaptation (Biology), Evolutionary adaptation, Microbial mutation

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Some recollections and reflections on mutation rates

Article Abstract:

Research work on mutants and mutation contributed to the advance of quantitative biology. Some of these studies focused on the occurrence of mutation prior to the selection process for detecting its products, the DNA's role in bacterial transformation and the molecular structure of the DNA. Other scientists conducted an investigation of the physiological aspects of mutation using the chemostat. The chemostat was utilized to measure the mutation rate for cells that grow at varying rates under tryptophan limitation.

Research, Usage, Gene mutations, Gene mutation, Chemostat

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Leber's hereditary optic neuropathy: the etiological role of a mutation in the mitochondrial cytochrome b gene

Article Abstract:

Leber's hereditary optic neuropathy is a mitochondrial genetic disease which presents as a delayed onset loss of central vision and formation of centrocecal scotomata. Its probable cause is a mutation at mtDNA nucleotide 15257 from the substitution of asparagine for aspartic acid residue at the position of 171 of the cytochrome b protein. Recent studies revealed that there are at least three other primary mutations within the respiratory chain as well as the existence of secondary mutations.

Health aspects, Evaluation, Mutation (Biology), Mutation, Genetic disorders, Letter to the Editor, Leber's congenital amaurosis

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