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Illustration of a transversion: each of the 8 nucleotide changes between a purine and a pyrimidine (in red). The 4 other changes are transitions (in blue).. Transversion, in molecular biology, refers to a point mutation in DNA in which a single (two ring) purine (A or G) is changed for a (one ring) pyrimidine (T or C), or vice versa. [1]
A point mutation is a genetic mutation where a single nucleotide base is changed, inserted or deleted from a DNA or RNA sequence of an organism's genome. [1] Point mutations have a variety of effects on the downstream protein product—consequences that are moderately predictable based upon the specifics of the mutation.
Illustration of a transition: each of the 4 nucleotide changes between purines or between pyrimidines (in blue). The 8 other changes are transversions (in red).. Transition, in genetics and molecular biology, refers to a point mutation that changes a purine nucleotide to another purine (A ↔ G), or a pyrimidine nucleotide to another pyrimidine (C ↔ T).
Gene conversion is the process by which one DNA sequence replaces a homologous sequence such that the sequences become identical after the conversion. [1] Gene conversion can be either allelic, meaning that one allele of the same gene replaces another allele, or ectopic, meaning that one paralogous DNA sequence converts another.
Each nucleotide is subject to one transition (e.g., T to C) and 2 transversions (e.g., T to A or T to G). Because a site (or a sequence) is subject to twice as many transversions as transitions, the total rate of transversions for a sequence may be higher even when the rate of transitions is higher on a per-path basis.
These nucleotides are then replaced by standard nucleotides, allowing for a broad distribution of nucleic acid mutations spread over the gene sequence with a preference to transversions and with a unique focus on consecutive point mutations, both difficult to generate by other mutagenesis techniques.
Transitions (A ↔ G or C ↔ T) are more common than transversions (purine (adenine or guanine)) ↔ pyrimidine (cytosine or thymine, or in RNA, uracil)). [17] Perhaps the most common type of mutation in humans is a change in the length of a short tandem repeat (e.g., the CAG repeats underlying various disease-associated mutations).
The missense mutations may be classed as point accepted mutations if the mutated protein is not rejected by natural selection. A point accepted mutation — also known as a PAM — is the replacement of a single amino acid in the primary structure of a protein with another single amino acid, which is accepted by the processes of natural selection.