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Non-allelic or non-alletic

I stumbled across the term in my Human Genetics textbook. It didn't explain it there, and a quick google search only showed scientific papers that refer to 'recombinations with non-allelic genes' without explaining what they are.

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It is my understanding that a non-allelic gene is one that affects another's traits, but is not as a typical dominant / recessive manner. If I am correct, this is the same thing as epistasis - meaning that one gene modifies how another is expressed. There exists epistatic genes for horse coat color. One gene is the coat color itself (horses may have either brown or red color alleles at this loci), the second gene is for a protein that allows the coat color gene to be expressed. For example, a horse has two brown alleles at the coat color locus. It also has a wild type gene in the second (modifier) position. This modifier allows the color brown to be expressed and the horse is brown. B/B, wt/wt --> Brown If the horse has the two brown alleles, but has a mutant allele at the modifier position, then coat color is not expressed and the horse is white. B/B, mt/mt --> white

Because the modifier alleles are separate genes from the coat color alleles, the two are non-allelic - yet they both affect the same trait in some way.

I hope this helps.

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    $\begingroup$ +1 This is also my understanding of terdon's link. I would argue that the name non-allelic gene is very poorly chosen though. Theoretically speaking there might not have any single gene that does not affect the phenotypic expression of other genes. And of course a non-allelic gene can be a non-allelic gene only if it is polymorphic (and have multiple alleles)! $\endgroup$
    – Remi.b
    Nov 28, 2013 at 8:04
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The context of the term "non-allelic" is non-allelic recombinations which means recombinations between genes that are not exactly alleles but have enough sequence homology to permit recombination.

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  • $\begingroup$ Is sequence homology needed for recombination? $\endgroup$
    – One Face
    Feb 17, 2015 at 8:19
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    $\begingroup$ @CRags For homologous recombination, yes. Even for other kinds of recombination (for e.g. VDJ) there is a stretch of sequence that acts as a homologous block. $\endgroup$
    – WYSIWYG
    Feb 17, 2015 at 9:08
  • $\begingroup$ Just to expand that recombination is not always needed: there is NJEH (Non-Homologous End Joining), which for example, is how CRISPR works. As it's name suggests in NHEJ, no sequence similarity is required and 2 DNA stretches are simply ligated together at their respective blunt faces. $\endgroup$
    – Joe Healey
    Jan 5, 2017 at 20:38
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From "Gene Interactions: Allelic and Non-Allelic" (biologydiscussion.com)

'Non-allelic or inter-allelic interactions … occur where the development of single character is due to two or more genes affecting the expression of each other in various ways.'

'Two non-allelic gene pairs affect the same character. The dominant allele of each of the two factors produces separate phenotypes when they are alone. When both the dominant alleles are present together, they produce a dis­tinct new phenotype. The absence of both the dominant alleles gives rise to yet another pheno­type.'

'When a gene or gene pair masks or prevents the expression of other non-allelic gene, called epistasis. The gene which produces the effect called epistatic gene and the gene whose expres­sion is suppressed called hypostatic gene.'

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From "Genetic Terminology" (ncbi.nlm.nih.gov)

'Whereas Drosophila geneticists used to talk of two loci for a gene, and human geneticists used to talk of two genes at a locus, modern geneticists talk of “two alleles of a gene” or “two alleles at a locus”; this last, which is nowadays so common, is the terminology that will thus be used in this book. It then follows (rather awkwardly) that two alleles at the same locus are allelic to each other, whereas two alleles that are at different loci are non-allelic to each other.'

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From slides "Interaction of genes" (slide_9) (slideshare.net)

'Non-Allelic gene interaction: In inter allelic genetic interactions, the independent (non homologous) genes located on the same or on different chromosomes interact with one another for the expression of single phenotypic trait of an organism.'

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