Sex Determination in Honeybees | Learn Science at Scitable

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In honey bees, the two sets of chromosomes must also have different alleles for a complementary sex determiner (csd) gene if the diploid is to develop into a female." /> <link rel="canonical" href="http://www.nature.com/scitable/topicpage/sex-determination-in-honeybees-2591764"/> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <script type="text/plain" data-cc-script="C04"> var initScriptsList = ["", "/natedjsp/scripts/commonScripts.jsp", "/natedjsp/empty.jsp", "/natedjsp/scripts/readingScript.jsp"]; var jsLoadMethod = "topicRoomLoad"; </script> <script data-cc-script="C04" data-src="/scitable/nated/natedjsp/scripts/jqueryAjaxScripts.js" type="text/javascript"></script> <link href="/scitable/nated/natedjsp/scripts/commonStylesEmbeddedFonts.css" rel="stylesheet" type="text/css" /> <link href="/scitable/nated/natedjsp/scripts/topicRoomStyles.css" rel="stylesheet" type="text/css" /> <meta name="WT.cg_n" content="Scitable" /> <meta name="WT.cg_s" content="Chromosomes and Cytogenetics" /> <meta name="WT.z_cg_cat" content="Sex Determination in Honeybees" /> <meta name="WT.z_cg_topic" content="Sex Determination in Honeybees" /> <meta name="WT.z_cg_level" content="MED" /> <style type="text/css">#right_Nav_header {display:none;}</style><script type="text/plain" data-cc-script="C04">function openPageLink(B){var A=document.getElementById(B).value;if(A!=""){location.href=A}}</script></head> <body class="specific-scitable"><p style="background-color: #333; color: #fff; text-align: center; padding: 10px; font-weight: 600; margin: 0; border-bottom: 1px solid #000">This page has been archived and is no longer updated</p> <script type="text/plain" data-cc-script="C04"> $(document).ready(function() { if(document.getElementById('facebookLink')!=null){ var replacements = new Array(); replacements[0] = '/'; replacements[1] = '%2F'; var fjs = document.getElementById('facebookLink'); var locationHref = replaceall(location.href,replacements); replacements[0] = ':'; replacements[1] = '%3A'; locationHref = replaceall(locationHref,replacements) fjs.src = fjs.src.replace('link',locationHref); } }); function replaceall( str, replacements ) { if(str=='' || str==null || str==undefined) { return ''; } var idx = str.indexOf( replacements[0] ); while ( idx > -1 ) { str = str.replace( replacements[0], replacements[1] ); idx = str.indexOf( replacements[0] ); } return str; } var googletag = googletag || {}; googletag.cmd = googletag.cmd || []; (function() { var gads = document.createElement('script'); gads.async = true; gads.type = 'text/javascript'; var useSSL = 'https:' == document.location.protocol; gads.src = (useSSL ? 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right: -20px; bottom: -2px;"> <div class="clearfix w100p hideForPrint"> <div class="fright padleft3px"> <a rel="nofollow" id="redditShareLink" href="http://www.reddit.com/submit?url=" onClick="shareWithReddit();return false;"><img class="nomargin borderNone pad2px" title="Share Using Reddit" src="/scitable/natedimages/reddit-share-icon.png"/></a> </div> <div class="fright padleft3px"> <a rel="nofollow" id="stumbleUponLink" href="#" onClick="shareWithStubmleUpon();return false;"><img class="nomargin borderNone pad2px" title="StumbleUpon" src="/scitable/natedimages/stumbleupon.png"/></a> </div> <div class="fright padleft3px"> <a rel="nofollow" id="googlePlusLink" href="https://plus.google.com/share?url=" onClick="shareWithGooglePlus();return false;"><img class="nomargin borderNone pad2px" title="Share with Google+" src="/scitable/natedimages/gplus-16.png"/></a> </div> <div class="fright padleft3px"> <a rel="nofollow" id="twitterShareLnk" href="http://twitter.com/share?url=" onClick="normalShareWithTwitter();return false;"><img class="nomargin borderNone pad2px" title="Share with Twitter" src="/scitable/natedimages/icon-twitter.jpg"/></a> </div> <div class="fright padleft3px"> <a rel="nofollow" id="faceBookShareLnk" href="http://www.facebook.com/share.php?u=" onClick="normalShareWithFaceBook();return false;"><img class="nomargin borderNone pad2px" title="Share with Facebook" src="/scitable/natedimages/icon-facebook.jpg" /></a> </div> <div class="fright padleft3px"> <a name="shareEMailSplashAnc" id="shareEMailSplashAnc" href="#" onClick="sendMailToShare('lnkLBMdlLIID', event);return false;"><img class="nomargin borderNone pad2px" src="/scitable/natedimages/email_icon.gif" alt="Email" /></a> </div> <div class="fright padleft3px"> <a href="javascript:printReadingPage()"><img title="Print" class="nomargin borderNone pad2px" src="/scitable/natedimages/print_15.gif"/></a> </div> <div class="fright padleft3px"> <a onMouseOver="return displayOnMouseOverText(this);" href="#" id="bookmarkTRArttAnc" name="bookmarkTRArttAnc" onclick="addToLocker(); return false;"><img title="Bookmark" class="nomargin borderNone pad2px" src="/scitable/natedimages/icon_bookmark.gif"/></a> </div> </div> </div> </div> </div> </div> <input type="hidden" name="isCoverPage" id="" value="N" /> </div> <div class="clear"></div> </div> <div class="clear"></div> </div> <div class="px18 normalFontWeight margintop10px readPgHdng" style="line-height: 26px ! important;">In humans, sex is determined by the presence or absence of X or Y sex chromosomes. In honeybees, however, evolution has resulted in a very different and unique sex determination system.</div> <div class="fright padright5px hideForPrint"> <a href="javascript:resizeFontScitable('fontSize11')" class="padright10px"><span class="px11 mousePointerHand lh22" id="sizeNo1">Aa</span></a> <a href="javascript:resizeFontScitable('fontSize15')" class="padright10px"><span class="px15 mousePointerHand lh22" id="sizeNo2">Aa</span></a> <a href="javascript:resizeFontScitable('fontSize20')" class="padright10px"><span class="mousePointerHand lh22 px20" id="sizeNo3">Aa</span></a> </div> <div class="clear"></div> <div class="articleHR w98p"></div> <div id="orgCnt"> <div id="trOutLine"></div> <div id="fontSizeChange" class="fontSizeChange"><div id="mainCntArtPageDiv"><div id="trPage"> <div class="articleContent"> <div class="clear"></div> <div class="contentSection"> <div class="sectionTitle"><h2 style="display:none;"> </h2></div> <div class="clear"></div> <div class="sectionParas"> <div class="paraArticle"> <div> <P>In honeybees (or honey bees), <span class="glossaryTermLink" onmouseover="showGloDescription("1431",this);return false;">sex</span> is normally determined by the <span class="glossaryTermLink" onmouseover="showGloDescription("538",this);return false;">fertilization</span> or non-fertilization of eggs, rather than the presence or absence of <span class="ontologyTermLink" onmouseover="showDescription("108",this);return false;">sex chromosomes</span>. This mode of <span class="ontologyTermLink" onmouseover="showDescription("99",this);return false;">sex determination</span> was first discovered by Johann Dzierzon, a Catholic priest, in 1845. Dzierzon reported that a virgin queen which has not taken a mating flight (the queens mate only while in free flight away from nest) produces only male <span class="glossaryTermLink" onmouseover="showGloDescription("1238",this);return false;">progeny</span> (Dzierzon <EM>et al., </EM>1945). His report was the first rigorous description of a sex determination system, occurring more than 50 years before the discovery of sex chromosomes (McClung, 1902; Wilson, 1905). We now know that honey bees are not unique and that about 20% of animal <span class="ontologyTermLink" onmouseover="showDescription("312",this);return false;">species</span> use a <span class="glossaryTermLink" onmouseover="showGloDescription("1961",this);return false;">haplodiploid</span> mode of <span class="ontologyTermLink" onmouseover="showDescription("27",this);return false;">reproduction</span>. In haplodiploid systems, male progeny normally develops from unfertilized eggs, which are <span class="ontologyTermLink" onmouseover="showDescription("309",this);return false;">haploid</span> and have just one set of chromosomes. The fertilized honey bee eggs, which are diploid and have two sets of chromosomes, differentiate into queens and worker bees.</P> </div> </div> <div class="clear"></div> </div> </div> <div class="clear"></div> <div class="contentSection"> <div class="sectionTitle"> <h2> <SECTIONTITLE-1>Complementary Sex Determination</SECTIONTITLE-1> </h2> </div> <div class="clear"></div> <div class="sectionParas"> <div class="paraArticle"> <div> <p><a name="anchEmbedImg_1235418235800-5827713119_1" ><input type="hidden" name="hidEmbedImg" id="hidEmbedImg_1235418235800-5827713119_1" value="/scitable"/><input type="hidden" name="hidEmbedPlayerState" id="hidEmbedPlayerState_1235418235800-5827713119_1" value="uninitedaudio"/></a><div style="width:136px;" class="imageSet Left"><div style="width:136px;"><A href="#" onclick="dispOrigImg("/scitable/content/ne0000/ne0000/ne0000/ne0000/2591145/gempe-honeybee-f1_FULL.jpg", "Sex determination in hymenoptera.", "true", "Figure 1", "Genotypes and sexual fate under the system of complementary sex determination found in many hymenopteran species (ants, bees, wasps, sawflies). Males derive from unfertilized eggs and have only one sex determination allele (marked by different colored bars). Fertilized eggs with two different sex-determining alleles (heterozygous) develop into females. Diploid males arise from fertilized eggs that are homozygous for the same sex-determining allele. These diploid males arise most commonly under inbreeding conditions in which the father has an allele in common with the mother.", "true", "All rights reserved.", '716', '549', 'http://www.nature.com/scitable');"><IMG src="/scitable/content/ne0000/ne0000/ne0000/ne0000/2591145/gempe-honeybee-f1_THUMB_0.jpg" title="" alt="A diagram shows the sex of the progeny in hymenoptera from hypothetical mating scenarios between a female, depicted as red rectangles, and two different males, depicted as blue rectangles. Arrows point from the parents to their respective offspring." /></A><br/><div class="imageCaption pipeblack bold" style="padding:10px;" ><A class="pipeblack bold" href="#" onclick="dispOrigImg("/scitable/content/ne0000/ne0000/ne0000/ne0000/2591145/gempe-honeybee-f1_FULL.jpg", "Sex determination in hymenoptera.", "true", "Figure 1", "Genotypes and sexual fate under the system of complementary sex determination found in many hymenopteran species (ants, bees, wasps, sawflies). Males derive from unfertilized eggs and have only one sex determination allele (marked by different colored bars). Fertilized eggs with two different sex-determining alleles (heterozygous) develop into females. Diploid males arise from fertilized eggs that are homozygous for the same sex-determining allele. These diploid males arise most commonly under inbreeding conditions in which the father has an allele in common with the mother.", "true", "All rights reserved.", '716', '549', 'http://www.nature.com/scitable');"><img class="fleft borderNone" alt="View Full-Size Image" src="/scitable/natedimages/plus_box.gif"/>Figure 1<div class="clear"></div><div class="nomargin padleft4px pipeblack bold fright textalignleft"><a title="Individuals are depicted as vertical rectangles: females are shown in red and males are shown in blue. Chromosomes are depicted as vertical black lines inside each rectangle. Some insects have two chromosomes, and others have a single chromosome. A point halfway down the length of each chromosome represents the sex determination locus (SDL). Each chromosome has a solid red bar, a white-striped red bar, or a red-spotted white bar. The different colored versions of the bar represent alleles, or different versions of the sex determination gene. A diploid female queen (top left) has two chromosomes: one has a red bar at the SDL, and one has a spotted bar at the SDL. If the queen does not mate with a male, her eggs will remain unfertilized. Haploid males (bottom left) may develop from these unfertilized eggs. One male (left) has a solid red bar at the SDL, whereas the second male has a red-spotted white bar at the SDL. Having a single allele at the sex determination locus means each of these individuals will develop into a male and are considered hemizygous. The queen may mate with the haploid male to her immediate right or to her far right. The male to her immediate right has a solid red bar at the SDL on his single chromosome. If a mating event occurs and the male fertilizes the queen's eggs, the fertilized eggs will develop into diploid progeny (bottom middle). The progeny at left has a solid red bar at the SDL on each of the two chromosomes. Because the allele for the sex determination gene is the same on both chromosomes, the offspring is a male and is considered homozygous. The progeny at right has a red-spotted white bar at the SDL on one chromosome and a red bar on the second chromosome. Because the allele for the sex determination gene is not the same on both chromosomes, the offspring is a female and is considered heterozygous. The male to the queen's far right has a striped red bar at the SDL on his single chromosome. If a mating event occurs and this male fertilizes the queen's eggs, the fertilized eggs will develop into two diploid female progeny (bottom right). The female progeny at left has a red bar at the SDL on one of her chromosomes and a white-striped red bar at the SDL on her second chromosome. The female progeny at right has a red-spotted white bar at the SDL on one of her chromosomes and a white-striped red bar at the SDL on her second chromosome.&nbsp; Because the allele for the sex determination gene is not the same on each of their chromosomes, both individuals are females and are considered heterozygous." href="javascript:void(0)" onclick="callNewShowInformAfterPublish("true","true","Y","/scitable/content/ne0000/ne0000/ne0000/ne0000/2591145/gempe-honeybee-f1_FULL.jpg", "Sex determination in hymenoptera.", "Figure 1", "Genotypes and sexual fate under the system of complementary sex determination found in many hymenopteran species (ants, bees, wasps, sawflies). Males derive from unfertilized eggs and have only one sex determination allele (marked by different colored bars). Fertilized eggs with two different sex-determining alleles (heterozygous) develop into females. Diploid males arise from fertilized eggs that are homozygous for the same sex-determining allele. These diploid males arise most commonly under inbreeding conditions in which the father has an allele in common with the mother.", '716','http://www.nature.com/scitable', "Individuals are depicted as vertical rectangles: females are shown in red and males are shown in blue. Chromosomes are depicted as vertical black lines inside each rectangle. Some insects have two chromosomes, and others have a single chromosome. A point halfway down the length of each chromosome represents the sex determination locus (SDL). Each chromosome has a solid red bar, a white-striped red bar, or a red-spotted white bar. The different colored versions of the bar represent alleles, or different versions of the sex determination gene. A diploid female queen (top left) has two chromosomes: one has a red bar at the SDL, and one has a spotted bar at the SDL. If the queen does not mate with a male, her eggs will remain unfertilized. Haploid males (bottom left) may develop from these unfertilized eggs. One male (left) has a solid red bar at the SDL, whereas the second male has a red-spotted white bar at the SDL. Having a single allele at the sex determination locus means each of these individuals will develop into a male and are considered hemizygous. The queen may mate with the haploid male to her immediate right or to her far right. The male to her immediate right has a solid red bar at the SDL on his single chromosome. If a mating event occurs and the male fertilizes the queen's eggs, the fertilized eggs will develop into diploid progeny (bottom middle). The progeny at left has a solid red bar at the SDL on each of the two chromosomes. Because the allele for the sex determination gene is the same on both chromosomes, the offspring is a male and is considered homozygous. The progeny at right has a red-spotted white bar at the SDL on one chromosome and a red bar on the second chromosome. Because the allele for the sex determination gene is not the same on both chromosomes, the offspring is a female and is considered heterozygous. The male to the queen's far right has a striped red bar at the SDL on his single chromosome. If a mating event occurs and this male fertilizes the queen's eggs, the fertilized eggs will develop into two diploid female progeny (bottom right). The female progeny at left has a red bar at the SDL on one of her chromosomes and a white-striped red bar at the SDL on her second chromosome. The female progeny at right has a red-spotted white bar at the SDL on one of her chromosomes and a white-striped red bar at the SDL on her second chromosome.&nbsp; Because the allele for the sex determination gene is not the same on each of their chromosomes, both individuals are females and are considered heterozygous.")" class="inlineLinks"> Figure Detail </a></div></A><div class="clear"></div></div></div></div><a name="anchEmbedImg_1235418235800-5827713119_2" ><input type="hidden" name="hidEmbedImg" id="hidEmbedImg_1235418235800-5827713119_2" value="/scitable"/><input type="hidden" name="hidEmbedPlayerState" id="hidEmbedPlayerState_1235418235800-5827713119_2" value="uninitedaudio"/></a><div style="width:141px;" class="imageSet Right"><div style="width:141px;"><IMG src="/scitable/content/ne0000/ne0000/ne0000/ne0000/2591396/gempe-honeybee-f2_THUMB_0.jpg" title="" alt="A photograph shows over thirty black and yellow striped honeybees crawling on a portion of a honeycomb. The honeycomb is composed of many rows of circular pores. Some of the pores are filled with a yellow substance, and some of the pores are empty and black." /><br/><div class="imageCaption pipeblack bold" style="padding:10px;" >Figure 2: <div class="imageCaption pipeblack bold nopad">Honeybee colony.</div><div class="imageLegend pipeblack nopad">Inbreeding produces colonies with reduced numbers of progeny. Diploid male larvae homozygous at the sex determination locus (SDL) are consumed shortly after they hatch, resulting in empty cells on brood combs.</div><div class="creditLine bold nopad">© 2009 <a target="_blank" href="http://www.nature.com/scitable" class="inlineLinks">Nature Education</a> All rights reserved. <a href='javascript:show_inform("Terms of Use", "You may reproduce this material, without modifications, in print or electronic form for your personal, non-commercial purposes or for non-commercial use in an educational environment.");' class="inlineLinks"><img class="nomargin infoImg nofloat" title="View Terms of Use" alt="View Terms of Use" height="13px" width="13px" src="/scitable/natedimages/info_icon.png" /></a></div><div class="clear"></div></div></div></div>In the years that followed the observation that honey bees lack sex chromosomes, investigators were surprised to discover that <span class="ontologyTermLink" onmouseover="showDescription("310",this);return false;">diploid</span> males appeared in <span class="glossaryTermLink" onmouseover="showGloDescription("772",this);return false;">inbreeding</span> studies with honey bees. The presence of these diploid males suggested that neither the fertilization process nor the haploid or diploid state of the <span class="glossaryTermLink" onmouseover="showGloDescription("454",this);return false;">egg</span> provides the primary signal for sex determination in honey bees (Mackensen, 1951). Since the appearance of diploid males was associated with inbreeding, investigators proposed a hypothesis of <span class="glossaryTermLink" onmouseover="showGloDescription("282",this);return false;">complementary</span> sex determination, in which a single sex determination <span class="glossaryTermLink" onmouseover="showGloDescription("876",this);return false;">locus</span> (SDL) determines the sexual fate (Whiting, 1933; Whiting, 1943). According to this hypothesis, fertilized eggs that are <span class="glossaryTermLink" onmouseover="showGloDescription("737",this);return false;">homozygous</span> at SDL differentiate into diploid males, while fertilized eggs that are <span class="glossaryTermLink" onmouseover="showGloDescription("698",this);return false;">heterozygous</span> at SDL develop into females. Fertile males are produced from the queen's unfertilized, haploid eggs, which are necessarily <span class="glossaryTermLink" onmouseover="showGloDescription("681",this);return false;">hemizygous</span> at the SDL (Figure 1). <span class="glossaryTermLink" onmouseover="showGloDescription("735",this);return false;">Homozygosity</span> at the SDL is lethal to males. The diploid males are eaten by worker bees shortly after they hatch from the egg. This results in a typical brood pattern in honey bee colonies that bee keepers refer to as shoot brood (Figure 2).</p> <p>The isolation of the sex determination locus in honey bees led to the identification of the <i>complementary sex determiner</i> (<i>csd</i>) <span class="ontologyTermLink" onmouseover="showDescription("29",this);return false;">gene</span> (Beye <i>et al</i>., 2003) (Figure 3A). The <i>csd </i>gene encodes a potential <span class="ontologyTermLink" onmouseover="showDescription("138",this);return false;">splicing</span> factor that exists in at least 15 allelic variants that differ on average in ~3% of their <span class="ontologyTermLink" onmouseover="showDescription("115",this);return false;">amino acid</span> residues (Hasselmann and Beye, 2004). The <i>csd </i>gene product is necessary for female <span class="ontologyTermLink" onmouseover="showDescription("250",this);return false;">development</span>, because inactivation of <i>csd</i> gene product in female embryos causes a full switch into male development (Beye <i>et al</i>., 2003). The target of the <i>csd</i> gene product was recently identified as the <i>feminizer </i>(<i>fem</i>) gene (Hasselmann <i>et al</i>., 2008) (Figure 3A). The <i>fem</i> transcript is splicing differently in males and females, so that only female cells have a functional <i>fem</i> gene product. In males, splicing introduces a stop <span class="ontologyTermLink" onmouseover="showDescription("155",this);return false;">codon</span> into the <i>fem</i> coding sequence. </p> </div> </div> <div class="clear"></div> <div class="paraArticle"> <div> <br> </div> </div> <div class="clear"></div> </div> </div> <div class="clear"></div> <div class="contentSection"> <div class="sectionTitle"> <h2> <SECTIONTITLE-1>Evolution of Complementary Sex Determination</SECTIONTITLE-1> </h2> </div> <div class="clear"></div> <div class="sectionParas"> <div class="paraArticle"> <div><a name="anchEmbedImg_1235417940773-9285092207_1" ><input type="hidden" name="hidEmbedImg" id="hidEmbedImg_1235417940773-9285092207_1" value="/scitable"/><input type="hidden" name="hidEmbedPlayerState" id="hidEmbedPlayerState_1235417940773-9285092207_1" value="uninitedaudio"/></a><div style="width:141px;" class="imageSet Left"><div style="width:141px;"><A href="#" onclick="dispOrigImg("/scitable/content/ne0000/ne0000/ne0000/ne0000/2591480/gempe-honeybee-f3_FULL.jpg", "The complementary sex determination pathway.", "true", "Figure 3", "The nature and evolution of the complementary sex determination pathway in honey bees. (A) In <i>csd</i> heterozygotes, <i>csd</i> (complementary sex determiner) gene products activate the downstream gene <i>fem</i> (feminizer), whose gene product is required for female development. In homo-/hemizygous animals, the <i>csd</i> gene product ensures male development by the default regulatory pathway, in which neither the <i>csd</i> nor <i>fem</i> gene products are activated. (B) The primary signal for sex determination, the <i>csd</i> gene, arose from the ancestral progenitor gene <i>fem</i> by gene duplication. The modern function of <i>csd</i> evolved by positive selection and fixation of new amino acid changes in the <i>Csd</i> protein.", "true", "All rights reserved.", '847', '553', 'http://www.nature.com/scitable');"><IMG src="/scitable/content/ne0000/ne0000/ne0000/ne0000/2591480/gempe-honeybee-f3_THUMB_0.jpg" title="" alt="A pathway diagram in panel A (yellow rectangle) shows how the activity of the csd and fem genes changes in heterozygous, homozygous, and hemizygous individuals to determine sex as represented by red, green and yellow rectangles. A diagram in panel B (light blue rectangle) shows how the ancestral fem gene evolved to form a copy of itself (green rectangle) and the modern csd gene (red rectangle) over time." /></A><br/><div class="imageCaption pipeblack bold" style="padding:10px;" ><A class="pipeblack bold" href="#" onclick="dispOrigImg("/scitable/content/ne0000/ne0000/ne0000/ne0000/2591480/gempe-honeybee-f3_FULL.jpg", "The complementary sex determination pathway.", "true", "Figure 3", "The nature and evolution of the complementary sex determination pathway in honey bees. (A) In <i>csd</i> heterozygotes, <i>csd</i> (complementary sex determiner) gene products activate the downstream gene <i>fem</i> (feminizer), whose gene product is required for female development. In homo-/hemizygous animals, the <i>csd</i> gene product ensures male development by the default regulatory pathway, in which neither the <i>csd</i> nor <i>fem</i> gene products are activated. (B) The primary signal for sex determination, the <i>csd</i> gene, arose from the ancestral progenitor gene <i>fem</i> by gene duplication. The modern function of <i>csd</i> evolved by positive selection and fixation of new amino acid changes in the <i>Csd</i> protein.", "true", "All rights reserved.", '847', '553', 'http://www.nature.com/scitable');"><img class="fleft borderNone" alt="View Full-Size Image" src="/scitable/natedimages/plus_box.gif"/>Figure 3<div class="clear"></div><div class="nomargin padleft4px pipeblack bold fright textalignleft"><a title="The alleles for the csd gene are represented as solid red rectangles or red-spotted white rectangles in panel A. An individual with a solid red allele and a red spotted allele (left) is heterozygous for the csd gene. In heterozygotes, csd is active. An individual with two solid red alleles (middle) is homozygous for the csd gene. An individual with a single solid red allele (right) and no other alleles is hemizygous for the csd gene. In homozygotes and hemizygotes, csd is inactive. An arrow pointing from an active csd gene in a heterozygote downward to a rectangle representing a fem gene (green rectangle) shows that an active csd gene activates fem and produces a female. There is no arrow pointing from the inactive csd gene in a homo- or hemizygote to the fem gene in that individual, indicating the fem gene is inactive without the activity of csd. An individual with an inactive fem gene is male. The ancestral fem gene, depicted as a horizontal green rectangle (left), was duplicated to form a copy of itself (green rectangle, bottom right) and the modern csd gene (red rectangle, top right) over time. A horizontal arrow pointing from left to right along the bottom of the diagram represents time. Arrows angle up and down to the csd and fem genes, respectively, and are labeled at top as gene duplication over time. The upward arrow from ancestral fem to csd is labeled as positive selection, and the downward arrow from ancestral fem to fem is labeled as purifying selection." href="javascript:void(0)" onclick="callNewShowInformAfterPublish("true","true","Y","/scitable/content/ne0000/ne0000/ne0000/ne0000/2591480/gempe-honeybee-f3_FULL.jpg", "The complementary sex determination pathway.", "Figure 3", "The nature and evolution of the complementary sex determination pathway in honey bees. (A) In <i>csd</i> heterozygotes, <i>csd</i> (complementary sex determiner) gene products activate the downstream gene <i>fem</i> (feminizer), whose gene product is required for female development. In homo-/hemizygous animals, the <i>csd</i> gene product ensures male development by the default regulatory pathway, in which neither the <i>csd</i> nor <i>fem</i> gene products are activated. (B) The primary signal for sex determination, the <i>csd</i> gene, arose from the ancestral progenitor gene <i>fem</i> by gene duplication. The modern function of <i>csd</i> evolved by positive selection and fixation of new amino acid changes in the <i>Csd</i> protein.", '847','http://www.nature.com/scitable', "The alleles for the <i>csd</i> gene are represented as solid red rectangles or red-spotted white rectangles in panel A. An individual with a solid red allele and a red spotted allele (left) is heterozygous for the <i>csd</i> gene. In heterozygotes, <i>csd</i> is active. An individual with two solid red alleles (middle) is homozygous for the <i>csd</i> gene. An individual with a single solid red allele (right) and no other alleles is hemizygous for the <i>csd</i> gene. In homozygotes and hemizygotes, <i>csd</i> is inactive. An arrow pointing from an active <i>csd</i> gene in a heterozygote downward to a rectangle representing a <i>fem</i> gene (green rectangle) shows that an active <i>csd</i> gene activates <i>fem</i> and produces a female. There is no arrow pointing from the inactive <i>csd</i> gene in a homo- or hemizygote to the <i>fem</i> gene in that individual, indicating the <i>fem</i> gene is inactive without the activity of <i>csd</i>. An individual with an inactive <i>fem</i> gene is male. The ancestral <i>fem</i> gene, depicted as a horizontal green rectangle (left), was duplicated to form a copy of itself (green rectangle, bottom right) and the modern <i>csd</i> gene (red rectangle, top right) over time. A horizontal arrow pointing from left to right along the bottom of the diagram represents time. Arrows angle up and down to the <i>csd</i> and <i>fem</i> genes, respectively, and are labeled at top as gene duplication over time. The upward arrow from ancestral <i>fem</i> to <i>csd</i> is labeled as positive selection, and the downward arrow from ancestral <i>fem</i> to <i>fem</i> is labeled as purifying selection.")" class="inlineLinks"> Figure Detail </a></div></A><div class="clear"></div></div></div></div>The complementary mode of sex determination occurs in a variety of hymenopteran species, including bees, wasps and ants, but not all these species rely on products of the <em>csd</em> gene for sex determination. Comparison of gene orthologs in other bee and wasp species showed that the<em> csd </em>gene<em> </em>arose recently<em> </em>by gene <span class="ontologyTermLink" onmouseover="showDescription("70",this);return false;">duplication</span> within the honey bee <span class="glossaryTermLink" onmouseover="showGloDescription("863",this);return false;">lineage</span> from a copy of the ancestral progenitor gene <em>feminizer</em> (<em>fem</em>) (Figure 3B). The <em>fem</em> gene remains a conserved component of sex determination pathways among insects. During the <span class="ontologyTermLink" onmouseover="showDescription("78",this);return false;">evolution</span> of honey bees, the <em>fem</em> gene has become the target of <em>csd</em> activity (Figure 3A). The <em>csd</em> gene has most likely acquired its modern <span class="glossaryTermLink" onmouseover="showGloDescription("563",this);return false;">function</span> by <span class="glossaryTermLink" onmouseover="showGloDescription("1793",this);return false;">adaptive evolution</span>. According to one <span class="glossaryTermLink" onmouseover="showGloDescription("960",this);return false;">model</span> (Figure 3B) (Hasselmann <em>et al</em>., 2008), duplication of the ancestral sex-determining <em>fem</em> gene was followed by <span class="ontologyTermLink" onmouseover="showDescription("94",this);return false;">positive selection</span> in one of the duplicates, favouring the presence of a new <span class="glossaryTermLink" onmouseover="showGloDescription("1663",this);return false;">upstream</span> signal that ultimately resulted in the novel sex determination system in the honey bees (Figure 3). The evolution of the <em>csd</em> gene is an example of how easily a new sex determination systems can arise by simple molecular changes of the existing genetic repertoire. The reduction of meiotic <span class="ontologyTermLink" onmouseover="showDescription("226",this);return false;">recombination</span> that is observed at the sex determination locus of the honey bee may also indicate that the <em>csd</em> gene will gradually degenerate over time (Charlesworth <em>et al</em>., 2005), which would again facilitate the evolution and positive <span class="ontologyTermLink" onmouseover="showDescription("61",this);return false;">selection</span> of alternative sex determination signals over evolutionary time scales in the honey bee lineage.</div> </div> <div class="clear"></div> </div> </div> <div class="clear"></div> </div> <div style="display:none" id="tykChk"></div> <div id="divSources"> <h2 class="sourcesHead nopad">References and Recommended Reading</h2> <hr class="topFivebotTen"> <div class="articleSourcesList articleSourcesListBig nopad" id="sourcesDisp"> <P>Beye, M., Hasselmann, M., Fondrk, M. K., Page, R. E. & Omholt, S. W. The gene <EM>csd </EM>is the primary signal for sexual development in the honeybee and encodes an SR-type protein. <EM>Cell</EM> <STRONG>114</STRONG>, 419-429 (2003). </P> <P>Charlesworth, D., Charlesworth, B. & Marais, G. Steps in the evolution of heteromorphic sex chromosomes. <EM>Heredity</EM> (2005).</P> <P>Dzierzon, J. Gutachten über die von Herrn Direktor Stöhr im ersten und zweiten Kapitel des General-Gutachtens aufgestellten Fragen. <EM>Eichstädter Bienenzeitung</EM> <STRONG>1</STRONG>, 109-113, 119-121 (1845).</P> <P>Hasselmann, M. & Beye, M. Signatures of selection among sex-determining alleles of the honey bee. <EM>Proc Natl Acad Sci U S A</EM> <STRONG>101</STRONG>, 4888-4893 (2004).</P> <P>Hasselmann, M.<EM> et al.</EM> Evidence for the evolutionary nascence of a novel sex determination pathway in honeybees. <EM>Nature</EM> <STRONG>454</STRONG>, 519-522 (2008). doi:10.1038/nature07052 (<a href='/scitable/content/Evidence-for-the-evolutionary-nascence-of-a-2591617' onClick="return isUDV('/content/Evidence-for-the-evolutionary-nascence-of-a-2591617');" title="link to article" class='' >link to article</a>)</P> <P>Mackensen, O. Viability and sex determination in the honey bee (<EM>Apis mellifera</EM> L.). <EM>Genetics</EM> <STRONG>36</STRONG>, 500-509 (1951).</P> <P>McClung, C. E. The accessory chromosome - sex determinant? <EM>Biol. Bull. Mar. Biol. Lab. , Woods Hole</EM> <STRONG>3</STRONG>, 43-84 (1902).</P> <P>Whiting, P. W. Selective fertilization and sex-determination in Hymenoptera. <EM>Science</EM> <STRONG>78</STRONG>, 537-538 (1933).</P> <P>Whiting, P. W. Multiple alleles in complementary sex determination of <EM>Habrobracon</EM>. <EM>Genetics</EM> <STRONG>28</STRONG>, 365-382 (1943).</P> <P>Wilson, E. B. The chromosomes in relation to determination of sex in insects. <EM>Science</EM> <STRONG>22</STRONG>, 500-502 (1905).</P> </div> </div> </div> </div></div> </div> <div class="hideForPrint"> <div class="clear"></div> <ul class="topicDetailsLeft hideForPrint "> <li><a href="#TB_inline?height=300&width=400&inlineId=trOutLine" title="Outline of this Article" class="thickbox inlineLinks">Outline</a></li> <li id="bar1">|</li> <li id="keywordHide"><a onMouseOver="return displayOnMouseOverText(this);" href="#url" id="keywordLnkTR" name="keywordLnkTR" onClick="loadContentTagsOnStartUp(event, 'keywordLnkTR'); return false;" class="inlineLinks">Keywords</a></li> <li id="bar2">|</li> <li id="shareHide"><a onMouseOver="return displayOnMouseOverText(this);" id="shareCntToTRLnk" name="shareCntToTRLnk" href="#" onClick="shareWithGrpNewLB(event, 'shareCntToTRLnk');return false;" class="inlineLinks">Add Content to Group</a></li> <li id="fdBKLBMdlAncID"><a href="#" onClick="showPostCommentFdbk(event, 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As a registered user you can have access to all content in Scitable, interact directly with community members, create a personal locker, start and join groups and discussions, and more"; var signINReqMsgNonLoggedINToolTip = "You have to be logged in to use this feature."; var collapseLabelPage = "View Fewer"; </script> <script type="text/plain" data-cc-script="C04"> var isTopicLandingPageFllg = ''; var topicID = '7'; var invToJoinGrpGrpID = ""; var currentPagerItem = 1; </script> <script type="text/plain" data-cc-script="C04"> var browserIs = ''; var topicID='7'; var contentPK = '2591764'; var clickedNodeType = ''; var clickedContentPK = ''; var topicPK = ''; var clickedTopicPK = ''; var defaultDisplay = ''; var fontSizeCookie = 'null'; var isUserLiggedIn = "" var currDate = ''; var currDay = ''; var currYear = ''; var currMonth = ''; var map = ''; var mon = ''; var viewMode = ''; var dateNumeric = ''; var today = new Date(currDate); var selected_day = currDay; var currWorkingDay; var yearviewcontext = 0; var printviewcontext = 0; var weekHref = ""; var monthHref = ""; var str_buffer = ""; var n_weekstart=0; var calMode = 'topic'; var previousMonthHref = baseURL+'calendar?action=viewCalendar&view='+viewMode+ '&calMode=' +calMode; var nextMonthHref = baseURL+'calendar?action=viewCalendar&view='+viewMode+ '&calMode=' +calMode; var dayHref = baseURL+'calendar?action=viewCalendar&view='+viewMode+ '&calMode=' +calMode; var isSameUser= ""; var zimbraIncludeFlag = ""; var isAuthTopicAdmin = ""; var isLMSReq = ""; var contentId = '2591764'; contentID = '2591764'; var isTopicRoom = true; var cleanUrlContextPath = "/scitable"; var cleanBaseURL = '/scitable'; forumId=''; var discussion = ''; topicID='7'; var urlLoc = 'chromosomes-and-cytogenetics-7'; var numMemberTopic = '217'; var artSubTypeRed = 'RED'; var numGroupTopics = ''; weblogId='7'; var articleCtxPath = '/scitable/nated'; var ratingLabel = ""; var rateLabel = ""; var elementPerPage = "4 "; var topicPageUrlPresent = "/scitable/topic/chromosomes-and-cytogenetics-7"; var urlParam = ""; var tykAsmtPk = ""; var tykAsmtVersion=""; var exceededAllowedRegisteredMsg = null; exceededAllowedRegisteredMsg = "The article you have selected is available only for signed in users. If you are not a member of Scitable, registration is free and easy. As a registered user you can have access to all content in Scitable, interact directly with community members, create a personal locker, start and join groups and discussions, and more."; function detach(clickedContentPKInner){ //postCookieData('7')) //var url= parent.baseURL + 'browse?action=displayVisualBrowse&topicPK=' + topicPK + '&detach=true&contentPK=' + contentPKInner + '&type=' + clickedNodeTypeInner + '&urlString=' + escape(urlString) + '&rootPk=' + rootPk + '&rootType=' + rootType + '&groupInfo=true&groupUrlString='+escape(groupUrlString); var trBaseURL = ''; if(baseURL != ''){ trBaseURL = baseURL; } else { trBaseURL = parent.baseURL; } var url= trBaseURL + 'browse?action=displayVisualBrowse&topicPK=' + 7 + '&detach=true&contentPK=' + clickedContentPKInner + '&type=article'; //alert(url); detatchVBScreen(url); } function detatchVBScreen(url) { var detachedWindow; //alert("Here :" +url); if(browserIs!= "IE"){ var browser = navigator.userAgent; if(browser.indexOf("Safari")>-1){ window.open(url, "VisualBrowse", "height=630, width=780, address=no, status=no, scrollbars=no, resizable=1"); } else{ window.open(url, "VisualBrowse", "height=610, width=770, resizable=1, address=no, status=no"); } } else{ window.open(url, "VisualBrowse", "height=610, width=760, resizable=0, address=no, status=no"); } } function moveHeaderBlock() { try { var str = document.getElementById('brandingBarTRMainBottom').innerHTML; if (str != null && str != '') { document.getElementById('brandingBarTRMainTop').innerHTML = str; document.getElementById('brandingBarTRMainBottom').innerHTML = ''; } } catch (e) {} try { document.getElementById('dummyTRFns').innerHTML = ''; } catch (e) {} } moveHeaderBlock(); function markReadProgressBar(coursePk,unitContentPK){ var url = baseURL + 'group?action=markBookContentAsRead&unitContentPK='+ unitContentPK; AjaxUtil.request(url, { onComplete: function(xmlHttpReq) { location.href = cleanBaseURL + "/ebooks/" + coursePk + "/" + unitContentPK; } }); } </script> <script type="text/plain" data-cc-script="C04"> var gaJsHost = (("https:" == document.location.protocol) ? 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