tag:blogger.com,1999:blog-1812431336777691886.post5659918617860310794..comments2024-02-29T03:57:00.088-05:00Comments on The Mermaid's Tale: Mendelian Inheritance: Basic Genetics or Basic Mistake? Part V.Anne Buchananhttp://www.blogger.com/profile/09212151396672651221noreply@blogger.comBlogger3125tag:blogger.com,1999:blog-1812431336777691886.post-66975830046211043912011-08-11T07:23:35.281-04:002011-08-11T07:23:35.281-04:00Do you think that we should we be talking in terms...Do you think that we should we be talking in terms of penetrance (along a spectrum of more or less) rather than using the terms dominant and recessive?Holly Dunsworthhttps://www.blogger.com/profile/05260104967932801186noreply@blogger.comtag:blogger.com,1999:blog-1812431336777691886.post-48068611970858097662011-08-02T08:22:39.971-04:002011-08-02T08:22:39.971-04:00I think the difference between our views is largel...I think the difference between our views is largely semantic. I would say alleles have a spectrum of effects, with most being very small to a few being large, and most being more but a few being less context-specific. The spectrum is largely quantitative rather than qualitative, and differs in detail for each trait and species. <br /><br />Mendelian dominance should not be treated as a qualitative ground state of nature as it is in most textbooks, which I believe inculcates students into confusing inheritance of genes and the nature of traits, which I believe leads to a lot of poor biology. And I think quantitative genetics should not be treated as a separate field, as it typically used to be and in some senses still is. <br /><br />I think most variation at most genes has little phenotypic effect (lethals being excepted though even those can be context-dependent). Even traditional dominance is sometimes, if not usually at least somewhat context dependent.<br /><br />I think this explains the under-performance of GWA, because that was based on false expectations. Actually, I think the idea of inbreeding and recessiveness is also oversold. Most isolates are not heavily burdened with recessive diseases overall, even though some arise that are much rarer in their parent population--and we treat them as inherently recessive, which may overlook context-dependency in that population at a genome background level. That would in my view also apply to inbreeding depression, which is genomwide but doesn't necessarily mean specific loci have classical dominance. <br /><br />In that sense, inbreeding depression is about statistical dominance, in the terminology we used in our post. I think the loss of variation genomewide by inbreeding can rightly account for the depression phenomenon without needing classical single-locus, single-allele inherent dominance, which was the main point of our posts (at least that was our intention).<br /><br />Genetic load is a different subject that is interesting and in a way the reverse of its sense in the classical population genetics of decades ago, when the term arose. It's a very important but I think unsolved issue. We may want to do a post or two on that, come to think of it.Ken Weisshttps://www.blogger.com/profile/02049713123559138421noreply@blogger.comtag:blogger.com,1999:blog-1812431336777691886.post-87525620049995690952011-08-02T04:31:59.821-04:002011-08-02T04:31:59.821-04:00That typically only a few genes are identified in ...<i>That typically only a few genes are identified in this way shows how relatively rare real dominance is--how far it is from being the baseline, basic nature of inheritance!</i><br /><br />I liked reading your posts, but at this point I disagree. GWA studies are relatively unsuccesful, because they often aim to find alleles associated with a certain disease, which are rare and typically <b>recessive</b>. Thus, it is in fact dominance that makes it hard to detect these alleles. Although I broadly agree that dominance is not a fixed property of an allele, I think that it can be quite stable across different genomic backgrounds. Dominance explains why we have a genetic load of recessive deleterious alleles, and why we see inbreeding depression as soon as the homozygosity increases.<br /><br />Apart from that, I think the point that genes are not traits is worth making. A long time ago, the botanist Wilhelm Johannsen introduced the perfectly fine terms "genotype" and "phenotype" to make this distinction clear. It probably won't harm to remind people of that.Corneelhttps://www.blogger.com/profile/02884855837357720225noreply@blogger.com