nih-gov/medlineplus.gov/genetics/understanding/howgeneswork/genelocation/index.html
2025-02-26 13:17:41 -05:00

493 lines
28 KiB
HTML
Raw Blame History

This file contains invisible Unicode characters

This file contains invisible Unicode characters that are indistinguishable to humans but may be processed differently by a computer. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.

This file contains Unicode characters that might be confused with other characters. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.

<!DOCTYPE html>
<html lang="en" id="understanding_genetics" class="nojs us" data-root="https://medlineplus.gov/">
<head>
<meta charset="utf-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
<meta http-equiv="window-target" content="_top" />
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1" />
<link rel="canonical" href="https://medlineplus.gov/genetics/understanding/howgeneswork/genelocation/" />
<link rel="alternate" hreflang="en" href="https://medlineplus.gov/genetics/understanding/howgeneswork/genelocation/" />
<link rel="alternate" hreflang="es" href="https://medlineplus.gov/spanish/genetica/entender/comofuncionangenes/genubicacion/" />
<meta name="ac-dictionary" content="medlineplus-ac-dictionary" />
<meta name="description" content="Geneticists use maps to describe the location of a gene on a chromosome. Learn more about this process and the two types of maps used." />
<link rel="shortcut icon" href="https://medlineplus.gov/images/favicon.ico" type="image/x-icon" />
<link rel="apple-touch-icon" href="https://medlineplus.gov/images/touch-icon.png" />
<meta property="fb:app_id" content="1042245625821448" />
<meta property="og:title" content="How do geneticists indicate the location of a gene?: MedlinePlus Genetics" />
<meta property="og:url" content="https://medlineplus.gov/genetics/understanding/howgeneswork/genelocation/" />
<meta property="og:image" content="https://medlineplus.gov/images/GenesWork_Share.jpg" />
<meta property="og:description" content="Geneticists use maps to describe the location of a gene on a chromosome. Learn more about this process and the two types of maps used." />
<meta name="twitter:card" content="summary_large_image" />
<meta name="twitter:site" content="@medlineplus" />
<meta name="twitter:creator" content="@medlineplus" />
<meta name="twitter:title" content="How do geneticists indicate the location of a gene?: MedlinePlus Genetics" />
<meta name="twitter:description" content="Geneticists use maps to describe the location of a gene on a chromosome. Learn more about this process and the two types of maps used." />
<meta name="twitter:image" content="https://medlineplus.gov/images/GenesWork_Share.jpg" />
<meta name="twitter:image:alt" content=""/>
<meta property="og:image:alt" content="" />
<title>How do geneticists indicate the location of a gene?: MedlinePlus Genetics</title>
<link rel="stylesheet" href="https://medlineplus.gov/css/common_new.css?1738957187669" />
<!--[if IE 8]> <link rel="stylesheet" href="https://medlineplus.gov/css/ie8/common.css"> <![endif]-->
<link rel="stylesheet" href="https://medlineplus.gov/uswds/css/uswds_styles.css" />
<link rel="stylesheet" href="https://medlineplus.gov/utilities/lostatic.css">
<script type="text/javascript">document.getElementsByTagName('html')[0].className = document.getElementsByTagName('html')[0].className.replace( /(?:^|\s)nojs(?!\S)/g , '').trim();</script>
<script src="https://medlineplus.gov/uswds/js/uswds-init.min.js" type="text/javascript"></script>
<script>(function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':
new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],
j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src=
'https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);
})(window,document,'script','dataLayer','GTM-MMVM77');</script>
</head>
<body>
<noscript><iframe src="https://www.googletagmanager.com/ns.html?id=GTM-MMVM77"
height="0" width="0" style="display:none;visibility:hidden" title="googletagmanager"></iframe></noscript>
<a name="top" id="top"></a>
<a class="hide-offscreen" href="#start">Skip navigation</a>
<section
class="usa-banner"
aria-label="Official website of the United States government"
>
<div class="usa-accordion">
<header class="usa-banner__header">
<div class="usa-banner__inner">
<div class="grid-col-auto">
<img
aria-hidden="true"
class="usa-banner__header-flag"
src="https://medlineplus.gov/uswds/img/us_flag_small.png"
alt=""
/>
</div>
<div class="grid-col-fill tablet:grid-col-auto" aria-hidden="true">
<p class="usa-banner__header-text">
An official website of the United States government
</p>
<p class="usa-banner__header-action">Heres how you know</p>
</div>
<button
type="button"
class="usa-accordion__button usa-banner__button"
aria-expanded="false"
aria-controls="gov-banner-default-default"
>
<span class="usa-banner__button-text">Heres how you know</span>
</button>
</div>
</header>
<div
class="usa-banner__content usa-accordion__content"
id="gov-banner-default-default"
>
<div class="grid-row grid-gap-lg">
<div class="usa-banner__guidance tablet:grid-col-6">
<img
class="usa-banner__icon usa-media-block__img"
src="https://medlineplus.gov/uswds/img/icon-dot-gov.svg"
role="img"
alt=""
aria-hidden="true"
/>
<div class="usa-media-block__body">
<p>
<strong>Official websites use .gov</strong><br />A
<strong>.gov</strong> website belongs to an official government
organization in the United States.
</p>
</div>
</div>
<div class="usa-banner__guidance tablet:grid-col-6">
<img
class="usa-banner__icon usa-media-block__img"
src="https://medlineplus.gov/uswds/img/icon-https.svg"
role="img"
alt=""
aria-hidden="true"
/>
<div class="usa-media-block__body">
<p>
<strong>Secure .gov websites use HTTPS</strong><br />A
<strong>lock</strong> (
<span class="icon-lock"
><svg
xmlns="http://www.w3.org/2000/svg"
width="52"
height="64"
viewBox="0 0 52 64"
class="usa-banner__lock-image"
role="img"
aria-labelledby="banner-lock-description-default"
focusable="false"
>
<title id="banner-lock-title-default">Lock</title>
<desc id="banner-lock-description-default">Locked padlock icon</desc>
<path
fill="#000000"
fill-rule="evenodd"
d="M26 0c10.493 0 19 8.507 19 19v9h3a4 4 0 0 1 4 4v28a4 4 0 0 1-4 4H4a4 4 0 0 1-4-4V32a4 4 0 0 1 4-4h3v-9C7 8.507 15.507 0 26 0zm0 8c-5.979 0-10.843 4.77-10.996 10.712L15 19v9h22v-9c0-6.075-4.925-11-11-11z"
/>
</svg> </span
>) or <strong>https://</strong> means youve safely connected to
the .gov website. Share sensitive information only on official,
secure websites.
</p>
</div>
</div>
</div>
</div>
</div>
</section>
<div id="mplus-wrap">
<header>
<div id="mplus-header">
<div id="mplus-orgs">
<a href="https://www.nih.gov/" class="nih-org" target="_blank" title="National Institutes of Health">
<img class="nihlogo" src="https://medlineplus.gov/images/nihlogo.png" alt="National Institutes of Health"/>
</a><a href="https://www.nlm.nih.gov/" target="_blank"> National Library of Medicine</a>
</div>
<div id="mplus-logo" class="years-25">
<a href="https://medlineplus.gov/">
<img alt="MedlinePlus Trusted Health Information for You" title="MedlinePlus Trusted Health Information for You" src="https://medlineplus.gov/images/m_logo_25.png"/>
</a>
</div>
<div id="mplus-nav">
<div aria-live="polite" class="sm-live-area hide-offscreen"></div>
<button id="sm-menu-btn" class="navmenu-btn" title="Menu" role="button" aria-controls="mplus-menu-list" type="submit">Menu<span class="icon icon-nav-menu"></span></button>
<ul id="mplus-menu-list" class="nav-list">
<li><a href="https://medlineplus.gov/healthtopics.html">Health Topics</a></li>
<li><a href="https://medlineplus.gov/druginformation.html">Drugs & Supplements</a></li>
<li><a href="https://medlineplus.gov/genetics/">Genetics</a></li>
<li><a href="https://medlineplus.gov/lab-tests/">Medical Tests</a></li>
<li><a href="https://medlineplus.gov/encyclopedia.html">Medical Encyclopedia</a></li>
<li><a href="https://medlineplus.gov/about/">About MedlinePlus</a></li>
</ul><button id="sm-search-btn" class="navmenu-btn" title="Search" role="button" aria-controls="mplus-search" type="submit"><span class="hide-offscreen"></span>Search<span class="icon icon-nav-search"></span></button>
<div class="top-1">
<form id="mplus-search" method="get" action="https://vsearch.nlm.nih.gov/vivisimo/cgi-bin/query-meta" title="Search MedlinePlus" target="_self">
<input type="hidden" name="v:project" value="medlineplus"/>
<input type="hidden" name="v:sources" value="medlineplus-bundle"/>
<div class="form-box text-combo">
<div class="form-area"><label class="hide-offscreen" for="searchtext_primary">Search MedlinePlus</label>
<input id="searchtext_primary" class="form-text" type="text" placeholder="Search MedlinePlus" alt="#Site Search input" title="Site Search input" maxlength="400" size="40" name="query" autocomplete="off" role="textbox" aria-autocomplete="list" aria-haspopup="true"/>
</div>
<div class="button-area">
<button class="form-btn" title="Search MedlinePlus" alt="Search MedlinePlus" type="submit">GO</button>
</div>
</div>
</form>
<div class="secondarynav">
<ul class="nav-list">
<li><a href="https://medlineplus.gov/about/"><span>About MedlinePlus</span></a></li>
<li><a href="https://medlineplus.gov/whatsnew/">What's New</a></li>
<li><a href="https://medlineplus.gov/sitemap.html"><span>Site Map</span></a></li>
<li><a href="https://support.nlm.nih.gov/knowledgebase/category/?id=CAT-01231&category=medlineplus&from=https%3A//medlineplus.gov/genetics/understanding/howgeneswork/genelocation/" target="_blank"><span>Customer Support</span></a></li>
</ul>
</div>
</div>
<div id="mplus-nav-bar">
<ul class="nav-list">
<li><a href="https://medlineplus.gov/healthtopics.html">Health Topics</a></li><li><a href="https://medlineplus.gov/druginformation.html">Drugs & Supplements</a></li><li><a href="https://medlineplus.gov/genetics/">Genetics</a></li><li><a href="https://medlineplus.gov/lab-tests/">Medical Tests</a></li><li><a href="https://medlineplus.gov/encyclopedia.html">Medical Encyclopedia</a></li>
</ul>
</div>
<a id="mplus-lang-toggle" href="https://medlineplus.gov/spanish/genetica/entender/comofuncionangenes/genubicacion/" title="Español">Español</a>
</div>
</div>
</header>
<div id="mplus-content">
<div id="breadcrumbs">
<div itemprop="breadcrumb" itemscope="" itemtype="http://schema.org/BreadcrumbList">
<span class="hide-offscreen">You Are Here:</span>
<div itemscope itemprop="itemListElement" itemtype="http://schema.org/ListItem">
<a href="https://medlineplus.gov/" itemprop="item"><span itemprop="name">Home</span></a>
&rarr;
<meta itemprop="position" content="1"/>
</div>
<div itemscope itemprop="itemListElement" itemtype="http://schema.org/ListItem">
<a href="https://medlineplus.gov/genetics/" itemprop="item"><span itemprop="name">Genetics</span></a>
&rarr;
<meta itemprop="position" content="2"/>
</div>
<div itemscope itemprop="itemListElement" itemtype="http://schema.org/ListItem">
<a href="https://medlineplus.gov/genetics/understanding/" itemprop="item"><span itemprop="name">Help Me Understand Genetics</span></a>
&rarr;
<meta itemprop="position" content="3"/>
</div>
<div itemscope itemprop="itemListElement" itemtype="http://schema.org/ListItem">
<a href="https://medlineplus.gov/genetics/understanding/howgeneswork/" itemprop="item"><span itemprop="name">How Genes Work</span></a>
&rarr;
<meta itemprop="position" content="4"/>
</div>
<div>
<span>How do geneticists indicate the location of a gene?</span>
</div>
</div>
</div>
<span class="page-url print-only">URL of this page: https://medlineplus.gov/genetics/understanding/howgeneswork/genelocation/</span>
<div >
<article>
<div class="page-info">
<div class="page-title">
<a name="start" id="start"></a>
<h1>How do geneticists indicate the location of a gene?</h1>
</div>
<div class="page-actions"></div>
<noscript><span class="js-disabled-message">To use the sharing features on this page, please enable JavaScript.</span></noscript>
</div>
<div class="main">
<section><div class="mp-content"><p>Geneticists use maps to describe the location of a particular gene on a chromosome. One type of map uses the cytogenetic location to describe a genes position. The cytogenetic location is based on a distinctive pattern of bands created when chromosomes are stained with certain chemicals. Another type of map uses the molecular location, which is a precise description of a gene's position on a chromosome. The molecular location is based on the sequence of DNA building blocks (nucleotides) that make up the chromosome.</p>
<h2>Cytogenetic location</h2>
<p>Geneticists use a standardized way of describing a gene's cytogenetic location. In most cases, the location describes the position of a particular band on a stained chromosome:</p>
<p>17q12</p>
<p>It can also be written as a range of bands, if less is known about the exact location:</p>
<p>17q12-q21</p>
<p>The combination of numbers and letters provide a gene's “address” on a chromosome. This address is made up of several parts:</p>
<ul><li><p>The chromosome on which the gene can be found. The first number or letter used to describe a gene's location represents the chromosome. Chromosomes 1 through 22 (the autosomes) are designated by their chromosome number. The sex chromosomes are designated by X or Y.</p></li></ul>
<ul><li><p>The arm of the chromosome. Each chromosome is divided into two sections (arms) based on the location of a narrowing (constriction) called the centromere. By convention, the shorter arm is called p, and the longer arm is called q. The chromosome arm is the second part of the gene's address. For example, 5q is the long arm of <a data-pid="20039" href="https://medlineplus.gov/genetics/chromosome/5/">chromosome 5</a>, and Xp is the short arm of the <a data-pid="20075" href="https://medlineplus.gov/genetics/chromosome/x/">X chromosome</a>.</p></li></ul>
<ul><li><p>The position of the gene on the p or q arm. The position of a gene is based on a distinctive pattern of light and dark bands that appear when the chromosome is stained in a certain way. The position is usually designated by two digits (representing a region and a band), which are sometimes followed by a decimal point and one or more additional digits (representing sub-bands within a light or dark area). The number indicating the gene position increases with distance from the centromere. For example: 14q21 represents position 21 on the long arm of <a data-pid="20057" href="https://medlineplus.gov/genetics/chromosome/14/">chromosome 14</a>. 14q21 is closer to the centromere than 14q22.</p></li></ul>
<p>Sometimes, the abbreviations “cen” or “ter” are also used to describe a gene's cytogenetic location. “Cen” indicates that the gene is very close to the centromere. For example, 16pcen refers to the short arm of <a data-pid="20061" href="https://medlineplus.gov/genetics/chromosome/16/">chromosome 16</a> near the centromere. “Ter” stands for terminus, which indicates that the gene is very close to the end of the p or q arm. For example, 14qter refers to the tip of the long arm, or the very end, of chromosome 14.</p>
<div class="mediaobject"><div class="caption"><p>The <a data-pid="17111" href="https://medlineplus.gov/genetics/gene/cftr/"><em>CFTR</em></a> gene is located on the long arm of <a data-pid="20043" href="https://medlineplus.gov/genetics/chromosome/7/">chromosome 7</a> at position 7q31.2.</p></div>
<div class="imagedata"><img alt="The CFTR gene is located on the long (q) arm of chromosome 7 at position 31.2." height="400" src="https://medlineplus.gov/images/PX00008G_PRESENTATION.jpeg" width="500"/></div>
<div class="image-credit">Credit: U.S. National Library of Medicine</div></div>
<h2>Molecular location</h2>
<p>The Human Genome Project, an international research effort completed in 2003, determined the sequence of nucleotides for each human chromosome. This sequence information allows researchers to provide a more specific address than the cytogenetic location for many genes. A genes molecular address pinpoints the location of that gene in terms of nucleotides. It describes the genes precise position on a chromosome and indicates the size of the gene. Knowing the molecular location also allows researchers to determine exactly how far a gene is from other genes on the same chromosome.</p>
<p>Different groups of researchers often present slightly different values for a genes molecular location. Researchers interpret the sequence of the human genome using a variety of methods, which can result in small differences in a genes molecular address. </p></div>
</section>
</div>
<div class="side">
<aside>
<section><div class="side-section"><div class="mp-content"><div class="section-header long-header">
<h2>For more information on genetic mapping:</h2>
</div>
<div class="section-body">
<p>The National Human Genome Research Institute explains <a href="https://www.genome.gov/about-genomics/fact-sheets/Genetic-Mapping-Fact-Sheet" target="_blank">how researchers create a genetic map</a>.<span class="desc-text"><img alt="From the National Institutes of Health" class="imgdesc" height="16" src="https://medlineplus.gov/images/nih.png" title="From the National Institutes of Health" width="25"/></span></p>
<p>Information about <a href="https://www.ncbi.nlm.nih.gov/guide/genomes-maps/" rel="noopener noreferrer" target="_blank">assembling and annotating the genome</a> is available from NCBI.<span class="desc-text"><img alt="From the National Institutes of Health" class="imgdesc" height="16" src="https://medlineplus.gov/images/nih.png" title="From the National Institutes of Health" width="25"/></span></p>
</div></div>
</div></section>
</aside>
</div>
<div class="bottom">
<section><div class="mp-exp mp-content"><h2>Topics in the How Genes Work chapter</h2><ul><li><a data-pid="20145" href="https://medlineplus.gov/genetics/understanding/howgeneswork/protein/">What are proteins and what do they do?</a></li><li><a data-pid="20147" href="https://medlineplus.gov/genetics/understanding/howgeneswork/makingprotein/">How do genes direct the production of proteins?</a></li><li><a data-pid="20149" href="https://medlineplus.gov/genetics/understanding/howgeneswork/geneonoff/">Can genes be turned on and off in cells?</a></li><li><a data-pid="20151" href="https://medlineplus.gov/genetics/understanding/howgeneswork/epigenome/">What is epigenetics?</a></li><li><a data-pid="20153" href="https://medlineplus.gov/genetics/understanding/howgeneswork/cellsdivide/">How do cells divide?</a></li><li><a data-pid="20155" href="https://medlineplus.gov/genetics/understanding/howgeneswork/genesanddivision/">How do genes control the growth and division of cells?</a></li><li>How do geneticists indicate the location of a gene?</li></ul><p><a data-pid="20081" href="https://medlineplus.gov/genetics/understanding/">Other chapters in Help Me Understand Genetics</a></p></div>
</section>
<section>
<!--
<div class="from-ghr">
<img src="https://medlineplus.gov/images/fromGHR.png" alt="From Genetics Home Reference" />
<p>Genetics Home Reference has merged with MedlinePlus. Genetics Home Reference content now can be found in the "Genetics" section of MedlinePlus. <a href="https://medlineplus.gov/about/general/genetics/newhome/">Learn more</a></p>
</div>
-->
<p>The information on this site should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health.</p>
</section>
</div>
</article>
</div>
<div id="citation-how-to">
<button><span>Learn how to cite this page</span></button>
</div>
</div>
<footer>
<div id="mplus-footer">
<div class="footer1">
<ul class="secondarynav">
<li><a href="https://medlineplus.gov/about/">About MedlinePlus</a></li>
<li><a href="https://medlineplus.gov/whatsnew/">What's New</a></li>
<li><a href="https://medlineplus.gov/sitemap.html">Site Map</a></li>
<li><a href="https://support.nlm.nih.gov/knowledgebase/category/?id=CAT-01231&category=medlineplus&from=https%3A//medlineplus.gov/genetics/understanding/howgeneswork/genelocation/" target="_blank"><span>Customer Support</span></a></li>
</ul>
<ul class="follow-footer">
<li>
<a href="https://medlineplus.gov/rss.html" class="follow-item">Subscribe to RSS<img src="https://medlineplus.gov/images/feed.png" class="social-media-toolkit-icon" alt="RSS" title="RSS"></a>
</li>
<li>
<span class="follow-label">Follow us</span>
<a href="https://twitter.com/medlineplus" class="follow-item" target="_blank">
<img src="https://medlineplus.gov/images/i_share_twitter.png" class="follow-icon" alt="X" title="X">
</a>
<a href="https://facebook.com/Mplus.gov/" class="follow-item" target="_blank">
<img src="https://medlineplus.gov/images/i_share_fb.png" class="follow-icon" alt="Facebook" title="Facebook">
</a>
<a href="https://www.instagram.com/mplusgov/" class="follow-item" target="_blank">
<img src="https://medlineplus.gov/images/Instagram_Glyph_Gradient_RGB.png" class="follow-icon" alt="Instagram" title="Instagram">
</a>
</li>
<li>
<a href="https://medlineplus.gov/social-media-toolkit/" class="social-media-toolkit-item">Social Media Toolkit<img src="https://medlineplus.gov/images/i_social_media_toolkit.png" class="social-media-toolkit-icon" alt="Social Media Toolkit" title="Social Media Toolkit"></a>
</li>
</ul>
</div>
<div class="footer2">
<ul>
<li><a href=" https://www.nlm.nih.gov/web_policies.html" target='_blank'>NLM Web Policies</a></li>
<li><a href="https://medlineplus.gov/about/using/usingcontent/" >Copyright</a></li>
<li><a href="https://medlineplus.gov/accessibility.html">Accessibility</a></li>
<li><a href="https://medlineplus.gov/about/using/criteria/">Guidelines for Links</a></li>
<li><a href="https://medlineplus.gov/plugins.html">Viewers & Players</a></li>
<li><a href="https://www.hhs.gov/vulnerability-disclosure-policy/index.html" target="_blank">HHS Vulnerability Disclosure</a></li>
<li><a href="https://medlineplus.gov/medlineplus-connect/">MedlinePlus Connect for EHRs</a></li>
<li><a href="https://medlineplus.gov/about/developers/">For Developers</a></li>
</ul>
<div class="address">
<a href="https://www.nlm.nih.gov" target="_blank">National Library of Medicine</a>
<span>8600 Rockville Pike, Bethesda, MD 20894</span>
<a href="https://www.hhs.gov" target="_blank">U.S. Department of Health and Human Services</a>
<a href="https://www.nih.gov" target="_blank">National Institutes of Health</a>
</div>
<div class="date">
<span id="lastupdate">Last updated March 26, 2021</span>
</div>
<div class="return-top"><a href="#top" title="Return to top"><img class="return-top-icon" alt="Return to top" src="https://medlineplus.gov/images/return-top.png"></a></div>
</div>
</div>
</footer>
</div>
<script src="https://medlineplus.gov/jslib/jquery-3.6.0.min.js" type="text/javascript"></script>
<script src="https://medlineplus.gov/jslib/mplus-frontend-controls-new.js" type="text/javascript"></script>
<script src="https://medlineplus.gov/jslib/mplus-share.js?id=1112022" type="text/javascript"></script>
<!--[if lte IE 9]><script src="//www.nlm.nih.gov/medlineplus/jslib/jquery.placeholder.js" type="text/javascript"></script><![endif]-->
<script src="https://medlineplus.gov/jslib/control.js" type="text/javascript"></script>
<script src="https://medlineplus.gov/uswds/js/uswds.min.js" type="text/javascript"></script>
</body>
</html>