{"id":237,"date":"2012-11-05T16:37:44","date_gmt":"2012-11-05T20:37:44","guid":{"rendered":"https:\/\/sites.owu.edu\/wolverton\/?page_id=237"},"modified":"2016-12-01T08:50:41","modified_gmt":"2016-12-01T13:50:41","slug":"linkage","status":"publish","type":"page","link":"https:\/\/sites.owu.edu\/wolverton\/teaching\/cell-bio\/linkage\/","title":{"rendered":"Linkage"},"content":{"rendered":"<p><!--:en--><\/p>\n<h2 id=\"links\">Links<\/h2>\n<p><a href=\"http:\/\/www.nature.com\/principles\/ebooks\/introduction-to-cell-biology-4570805\/4569984\">Principles Module 44<\/a><\/p>\n<h2 id=\"objectives\">Objectives<\/h2>\n<ul>\n<li>Describe the conditions under which characters fail to assort independently<\/li>\n<li>Explain a test cross and how one is carried out<\/li>\n<li>Analyze the results of a test cross and calculate genetic distance<\/li>\n<\/ul>\n<h2 id=\"keypoints\">Key points<\/h2>\n<p>Background<\/p>\n<ul>\n<li>sometimes characters don&#8217;t assort independently during meiosis<\/li>\n<li>these characters show a high probability of being inherited together<\/li>\n<li>characters that travel together during meiosis are <strong>linked<\/strong><\/li>\n<\/ul>\n<div>Genetic mapping<\/div>\n<div>\n<ul>\n<li>linkage can be identified and quantified by careful observation of inheritance patterns<\/li>\n<li>the basis of genetic mapping is recombination due to crossing over<\/li>\n<li>characters that are located very close to each other on the chromosome have a lower probability of being separated by crossovers than those that are farther apart<\/li>\n<li>the frequency of crossovers can be used as a measure of distance between characters<\/li>\n<\/ul>\n<div>Performing a test cross<\/div>\n<div>\n<ul>\n<li>cross a known heterozygous individual with a known homozygous recessive individual<\/li>\n<li>score the number of offspring having each of the 4 possible phenotypes<\/li>\n<\/ul>\n<div>Example test cross<\/div>\n<div>\n<ul>\n<li>cross a homozygous recessive mutant for body color (black, b) and wing shape (vestigial, vg) with a fly heterozygous for both characters: bb vgvg \u00a0x \u00a0b+ vg+ \u00a0(the + represents the wild-type allele)<\/li>\n<li>phenotypes of offspring<\/li>\n<ul>\n<li>parental: black body, vestigial wings (405)<\/li>\n<li>parental: wild-type body and wings (415)<\/li>\n<li>recombinant: wild-type body, vestigial wings (92)<\/li>\n<li>recombinant: black body, wild-type wings (88)<\/li>\n<\/ul>\n<li>calculate recombination frequency<\/li>\n<ul>\n<li>(92 + 88) \/ 1000 = 0.18 or 18 map units<\/li>\n<\/ul>\n<li>notes<\/li>\n<ul>\n<li>the <em>only way<\/em>\u00a0to produce offspring with wild-type bodies and vestigial wings is via recombination<\/li>\n<li>the <em>only way<\/em>\u00a0to produce offspring with black bodies and wild-type wings is via recombination<\/li>\n<\/ul>\n<\/ul>\n<\/div>\n<\/div>\n<\/div>\n<h2 id=\"in-classactivities\">In-class activities<\/h2>\n<ul>\n<li>work through example test crosses<\/li>\n<\/ul>\n<h2 id=\"questionsforpractice\">Questions for Practice<\/h2>\n<ul>\n<li>Describe how you would test two characters for linkage. What predictions would you make about number of offspring for each phenotype if the genes are linked or not?<\/li>\n<\/ul>\n<p><!--:--><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Links Principles Module 44 Objectives Describe the conditions under which characters fail to assort independently Explain a test cross and how one is carried out Analyze the results of a test cross and calculate genetic distance Key points Background sometimes characters don&#8217;t assort independently during meiosis these characters show a high probability of being inherited [&hellip;]<\/p>\n","protected":false},"author":40,"featured_media":0,"parent":447,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-237","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/sites.owu.edu\/wolverton\/wp-json\/wp\/v2\/pages\/237","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/sites.owu.edu\/wolverton\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/sites.owu.edu\/wolverton\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/sites.owu.edu\/wolverton\/wp-json\/wp\/v2\/users\/40"}],"replies":[{"embeddable":true,"href":"https:\/\/sites.owu.edu\/wolverton\/wp-json\/wp\/v2\/comments?post=237"}],"version-history":[{"count":1,"href":"https:\/\/sites.owu.edu\/wolverton\/wp-json\/wp\/v2\/pages\/237\/revisions"}],"predecessor-version":[{"id":505,"href":"https:\/\/sites.owu.edu\/wolverton\/wp-json\/wp\/v2\/pages\/237\/revisions\/505"}],"up":[{"embeddable":true,"href":"https:\/\/sites.owu.edu\/wolverton\/wp-json\/wp\/v2\/pages\/447"}],"wp:attachment":[{"href":"https:\/\/sites.owu.edu\/wolverton\/wp-json\/wp\/v2\/media?parent=237"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}