{"id":1433,"date":"2020-08-06T23:54:56","date_gmt":"2020-08-06T23:54:56","guid":{"rendered":"https:\/\/meddists.com\/learn\/pre-clinical\/medical-genetics\/transmission-genetics\/deviations-from-mendelian-genetics\/"},"modified":"2021-01-31T23:21:32","modified_gmt":"2021-01-31T22:21:32","slug":"deviations-from-mendelian-genetics","status":"publish","type":"page","link":"https:\/\/meddists.com\/learn\/pre-clinical\/medical-genetics\/transmission-genetics\/deviations-from-mendelian-genetics\/","title":{"rendered":"Deviations from Mendelian Genetics"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\"><div class=\"intro\">Mendel&#8217;s laws discussed previously are only true if<\/p>\n\n\n\n<ol class=\"wp-block-list\"><li>The genes are carried on the <strong>autosomes<\/strong>. The rules do not apply for X-linked or Y-linked traits<\/li><li>It is a<strong> diploid<\/strong> organism that reproduces sexually<\/li><li>The traits are<strong> monogenic<\/strong> i.e determined by one gene<\/li><li>There is a large number of offspring<\/li><li>There is no gene interaction, recombination and\/or linkage<\/div><\/li><\/ol>\n\n\n\n<p class=\"wp-block-paragraph\">Exceptions to these rules are:<\/p>\n\n\n<span class=\"block-heading\" id=\"header_1\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title1\">Incomplete Dominance<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_1\">\n\n\n<p class=\"wp-block-paragraph\"><em>Details on incomplete dominance are discussed in detail in the Transmission Genetics: Mendelian Genetics: Introduction and important terms course<\/em><\/p>\n\n\n<\/span><span class=\"block-heading\" id=\"header_2\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title1\">Codominance<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_2\">\n\n\n<p class=\"wp-block-paragraph\"><em>Details on codominance are discussed in detail in the Transmission Genetics: Mendelian Genetics: Introduction and important terms course<\/em><\/p>\n\n\n<\/span><span class=\"block-heading\" id=\"header_3\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title1\">Genetic heterogeneity<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_3\">\n\n\n<p class=\"wp-block-paragraph\">This is when the same or very similar phenotypes are produced by different types and location of mutations. It has two components;<strong> allelic and locus heterogeneity<\/strong>.<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>Allelic heterogeneity is when different mutations in the same loci give rise to the same or similar phenotypes.<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Examples include <strong>alkaptonuria, phenylketonuria, albinism and achondroplasia<\/strong>.<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>Locus heterogeneity is when mutations in different genes at different loci give rise to the same phenotype.<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Examples include <strong>retinitis pigmentosa, familial hypercholesterolemia, xeroderma pigmentosum and osteogenesis imperfecta.<\/strong><\/p>\n\n\n<\/span><span class=\"block-heading\" id=\"header_4\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title1\">Phenotypic heterogeneity<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_4\">\n\n\n<p class=\"wp-block-paragraph\">This is when different mutations in different genes give rise to different phenotypes.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">An example is <strong>Hirschprung disease<\/strong>.<\/p>\n\n\n<\/span><span class=\"block-heading\" id=\"header_5\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title1\">Sex influenced disorders<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_5\">\n\n\n<p class=\"wp-block-paragraph\">These are disorders that although they are transmitted autosomally, they are expressed with different severities in the different sexes.<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>An example is a mutation in the <strong>HFE gene<\/strong> that causes <strong>hemochromatosis<\/strong>(iron overload). It is more severe in males as females tend to have a lower iron level than males due to a lower intake in the diet and loss of iron(in the blood) every month through menstruation.<\/li><li>Another example is some <strong>autoimmune diseases such as Systemic Lupus Erythematosus (SLE)<\/strong> that is more common in women due to the presence of estrogen.<\/li><\/ul>\n\n\n<\/span><span class=\"block-heading\" id=\"header_6\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title1\">Age of Onset<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_6\">\n\n\n<p class=\"wp-block-paragraph\">The age of onset can be<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>Very Early Onset: in this case, they appear before the child is born. They are known as <strong>lethal disorders<\/strong> and cause spontaneous abortions<\/li><li>Early Onset:&nbsp; in this case, the child is born with it and they are observed at birth. They are known as <strong>congenital disorders. <\/strong>An example is <strong>Tetralogy of Fallot.<\/strong><\/li><li>Late-onset: in this case, they appear later on in life. They are known as <strong>late-onset disorders<\/strong>. An example is<strong> Huntington Disease<\/strong>.<\/li><\/ul>\n\n\n<\/span><span class=\"block-heading\" id=\"header_7\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title1\">Epistasis<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_7\">\n\n\n<p class=\"wp-block-paragraph\"><em>Details on epistasis are discussed in detail in the Transmission Genetics: Epistasis course<\/em><\/p>\n\n\n<\/span><span class=\"block-heading\" id=\"header_8\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title1\">Incomplete penetrance<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_8\">\n\n\n<p class=\"wp-block-paragraph\"><em>Details on incomplete penetrance are discussed in detail in the Transmission Genetics: Mendelian Genetics: Introduction and important terms course<\/em><\/p>\n\n\n<\/span><span class=\"block-heading\" id=\"header_9\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title1\">Variable expressivity<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_9\">\n\n\n<p class=\"wp-block-paragraph\"><em>Details on variable expressivity are discussed in detail in the Transmission Genetics: Mendelian Genetics: Introduction and important terms course<\/em><\/p>\n\n\n<\/span><span class=\"block-heading\" id=\"header_10\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title1\">Polymorphisms<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_10\">\n\n\n<p class=\"wp-block-paragraph\"><em>Details on Polymorphisms are discussed in detail in the Polymorphisms course<\/em><\/p>\n\n\n<\/span><span class=\"block-heading\" id=\"header_11\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title1\">Linked genes<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_11\">\n\n\n<p class=\"wp-block-paragraph\"><em>Details on linked genes are discussed in detail in the Transmission Genetics: Linked and Recombinant Genes course<\/em><\/p>\n<\/span><div id=\"the_titles\" style=\"display:none;\"><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Incomplete Dominance<\/h4><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Codominance<\/h4><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Genetic heterogeneity<\/h4><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Phenotypic heterogeneity<\/h4><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Sex influenced disorders<\/h4><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Age of Onset<\/h4><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Epistasis<\/h4><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Incomplete penetrance<\/h4><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Variable expressivity<\/h4><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Polymorphisms<\/h4><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Linked genes<\/h4><\/div>","protected":false},"excerpt":{"rendered":"<p>Exceptions to these rules are: Incomplete Dominance Details on incomplete dominance are discussed in detail in the Transmission Genetics: Mendelian Genetics: Introduction and important terms course Codominance Details on codominance are discussed in detail in the Transmission Genetics: Mendelian Genetics: Introduction and important terms course Genetic heterogeneity This is when the same or very similar [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":1346,"menu_order":3,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-1433","page","type-page","status-publish","hentry"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.8 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Deviations from Mendelian Genetics &#8211; 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