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Non-allelic homologous recombination (NAHR) is a form of homologous recombination that occurs between two lengths of DNA that have high sequence similarity, but are not alleles. [ 1 ] [ 2 ] [ 3 ] It usually occurs between sequences of DNA that have been previously duplicated through evolution, and therefore have low copy repeats (LCRs).
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.
These rules (patterns) are not without exceptions. Non-allelic mutants may occasionally fail to complement (this is known as "non-allelic non-complementation" or "unlinked non-complementation"). This is an uncommon occurrence that depends on the type of mutants being investigated. Two mutations, for example, could be synthetically dominant ...
Another form of non-Mendelian inheritance is known as infectious heredity. Infectious particles such as viruses may infect host cells and continue to reside in the cytoplasm of these cells. If the presence of these particles results in an altered phenotype, then this phenotype may be subsequently transmitted to progeny. [13]
Coalescent theory is a model of how alleles sampled from a population may have originated from a common ancestor.In the simplest case, coalescent theory assumes no recombination, no natural selection, and no gene flow or population structure, meaning that each variant is equally likely to have been passed from one generation to the next.
Fitness epistasis (an interaction between non-allelic genes) is positive (in other words, diminishing, antagonistic or buffering) when a loss of function mutation of two given genes results in exceeding the fitness predicted from individual effects of deleterious mutations, and it is negative (that is, reinforcing, synergistic or aggravating ...
In 1998 it was determined that homologous pairing in Drosophila occurs through independent initiations (as opposed to a directed, 'processive zippering' motion). [4] [8]The first RNAi screen (based on DNA FISH [9]) was carried out to identify genes regulating D. melanogaster somatic pairing in 2012, [10] described at the time as providing "an extensive “parts list” of mostly novel factors".
Allelic exclusion is a process by which only one allele of a gene is expressed while the other allele is silenced. [1] This phenomenon is most notable for playing a role in the development of B lymphocytes , where allelic exclusion allows for each mature B lymphocyte to express only one type of immunoglobulin .