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The obvious inference from these experiments was that each gene mutation affects the activity of a single enzyme. This led directly to the one gene–one enzyme hypothesis, which, with certain qualifications and refinements, has remained essentially valid to the present day.
The two possibilities tested by the Luria–Delbrück experiment. (A) If mutations are induced by the media, roughly the same number of mutants are expected to appear on each plate. (B) If mutations arise spontaneously during cell divisions prior to plating, each plate will have a highly variable number of mutants.
DNA may be modified, either naturally or artificially, by a number of physical, chemical and biological agents, resulting in mutations. Hermann Muller found that "high temperatures" have the ability to mutate genes in the early 1920s, [2] and in 1927, demonstrated a causal link to mutation upon experimenting with an x-ray machine, noting phylogenetic changes when irradiating fruit flies with ...
Trinucleotide repeat expansion, is a DNA mutation that is responsible for causing any type of disorder classified as a trinucleotide repeat disorder. These disorders are progressive and affect the sequences of the human genome, frequently within the nervous system.
A mutation accumulation (MA) experiment is a genetic experiment in which isolated and inbred lines of organisms (so-called MA lines) are maintained such that the effect of natural selection is minimized, with the aim of quantitatively estimating the rates at which spontaneous mutations (mutations not caused by exogenous mutagens) occur in the studied organism.
Mutations in neuronal stem cells (especially during neurogenesis) [18] and in post-mitotic neurons lead to genomic heterogeneity of neurons—referred to as "somatic brain mosaicism". [3] The accumulation of age-related mutations in neurons may be linked to neurodegenerative diseases, including Alzheimer's disease, but the association is ...
The permissive temperature is the temperature at which a temperature-sensitive mutant gene product takes on a normal, functional phenotype. [2] When a temperature-sensitive mutant is grown in a permissive condition, the mutant gene product behaves normally (meaning that the phenotype is not observed), even if there is a mutant allele present.
His statistical evidence and the closely related idea of eugenics have long since been abandoned by the scientific community, but the concept that physical traits may affect the likelihood of criminal or unethical behavior in a person still has some scientific support. [32]