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Since all polymorphism has a genetic basis, genetic polymorphism has a particular meaning: Genetic polymorphism is the simultaneous occurrence in the same locality of two or more discontinuous forms in such proportions that the rarest of them cannot be maintained just by recurrent mutation or immigration, originally defined by Ford (1940).
A well accepted example of pleomorphism is Helicobacter pylori, which exists as both a helix-shaped form (classified as a curved rod) and a coccoid form. [7] Legionella pneumophila, the species of intracellular bacteria parasite responsible for Legionnaire's disease, has been seen to differentiate within a developmentally diverse network. [8]
A polymorphism can be any sequence difference. Examples include: Single nucleotide polymorphisms (SNPs) are a single nucleotide changes that happen in the genome in a particular location. The single nucleotide polymorphism is the most common form of genetic variation. [15]
An example would be a seemingly silent mutation in the multidrug resistance gene 1 , which codes for a cellular membrane pump that expels drugs from the cell, can slow down translation and allow the peptide chain to fold into an unusual conformation, causing the mutant pump to be less functional (in MDR1 protein e.g. C1236T polymorphism changes ...
Genetic markers can be used to study the relationship between an inherited disease and its genetic cause (for example, a particular mutation of a gene that results in a defective protein). It is known that pieces of DNA that lie near each other on a chromosome tend to be inherited together.
Mutations that lead to antigenic differences can be traced to the biochemical nature of the amino acid substitutions as well as the location of the mutation in the domain III. For example, substitutions at different amino acids results in varying levels of neutralization by antibodies. If mutation in a critical amino acid can dramatically alter ...
An example of a botanical genetic polymorphism is heterostyly, in which flowers occur in different forms with different arrangements of the pistils and the stamens. The system is called heteromorphic self-incompatibility , and the general 'strategy' of stamens separated from pistils is known as herkogamy .
Mutation rates can also differ even between genotypes of the same species; for example, bacteria have been observed to evolve hypermutability as they adapt to new selective conditions. [13] These different rates of nucleotide substitution are measured in substitutions ( fixed mutations ) per base pair per generation.