{"id":256637,"date":"2025-07-16T11:46:34","date_gmt":"2025-07-16T11:46:34","guid":{"rendered":"https:\/\/learnexams.com\/blog\/?p=256637"},"modified":"2025-07-16T11:46:37","modified_gmt":"2025-07-16T11:46:37","slug":"in-humans-red-green-color-blindness-is-controlled-by-a-gene-on-the-x-chromosome","status":"publish","type":"post","link":"https:\/\/www.learnexams.com\/blog\/2025\/07\/16\/in-humans-red-green-color-blindness-is-controlled-by-a-gene-on-the-x-chromosome\/","title":{"rendered":"In humans, red-green color-blindness is controlled by a gene on the X chromosome."},"content":{"rendered":"\n<p>In humans, red-green color-blindness is controlled by a gene on the X chromosome. For females, normal color vision is dominant to color-blindness. A convenient way to represent the gene is to use an X (for the X chromosome) with a superscript for the particular allele. Thus, if we use the letter &#8220;B&#8221; for the normal gene, the normal allele would be X^B and the color-blindness allele would be X^e. Genotypes are listed below. What are the phenotypes with respect to sex and color vision of each? X^B X^B &#8211; female with normal color vision X^B X^b &#8211; color-blind man Based on this, draw your own Punnett square on your own paper to determine their possible offspring. Submit a picture of your work with this assignment. What is the probability (out of 4) that they will have a color-blind daughter? What is the probability (out of 4) that they will have a color-blind son?<\/p>\n\n\n\n<p><strong><mark style=\"background-color:rgba(0, 0, 0, 0)\" class=\"has-inline-color has-ast-global-color-1-color\">The Correct Answer and Explanation is:<\/mark><\/strong><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Correct Answer:<\/h3>\n\n\n\n<p><strong>Genotypes and Phenotypes:<\/strong><\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>X\u1d2e X\u1d2e<\/strong> \u2013 Female with normal color vision<\/li>\n\n\n\n<li><strong>X\u1d47 Y<\/strong> \u2013 Male with color blindness<\/li>\n<\/ol>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">Punnett Square Cross:<\/h3>\n\n\n\n<p><strong>Parent Genotypes:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Mother: X\u1d2e X\u1d2e<\/li>\n\n\n\n<li>Father: X\u1d47 Y<\/li>\n<\/ul>\n\n\n\n<p>Now let&#8217;s set up the Punnett Square:<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th><\/th><th>X\u1d2e (mother)<\/th><th>X\u1d2e (mother)<\/th><\/tr><\/thead><tbody><tr><td>X\u1d47 (father)<\/td><td>X\u1d2e X\u1d47<\/td><td>X\u1d2e X\u1d47<\/td><\/tr><tr><td>Y (father)<\/td><td>X\u1d2e Y<\/td><td>X\u1d2e Y<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">Offspring Genotypes and Phenotypes:<\/h3>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>X\u1d2e X\u1d47<\/strong> \u2013 Female, normal vision (carrier, not color-blind)<\/li>\n\n\n\n<li><strong>X\u1d2e X\u1d47<\/strong> \u2013 Female, normal vision (carrier)<\/li>\n\n\n\n<li><strong>X\u1d2e Y<\/strong> \u2013 Male, normal vision<\/li>\n\n\n\n<li><strong>X\u1d2e Y<\/strong> \u2013 Male, normal vision<\/li>\n<\/ol>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">Final Probabilities:<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Probability of a color-blind daughter = 0 out of 4 = 0%<\/strong><\/li>\n\n\n\n<li><strong>Probability of a color-blind son = 0 out of 4 = 0%<\/strong><\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">Explanation <\/h3>\n\n\n\n<p>In humans, red-green color blindness is a <strong>sex-linked recessive trait<\/strong>, meaning the gene responsible is found on the <strong>X chromosome<\/strong> and not on the Y. Males (XY) only need one copy of the color-blind gene (X\u1d47) to express the trait, while females (XX) need <strong>two copies<\/strong> (X\u1d47 X\u1d47) to be color blind. If a female has only <strong>one X\u1d47<\/strong>, she will be a <strong>carrier<\/strong> but will still have normal vision.<\/p>\n\n\n\n<p>In this problem, the mother is <strong>X\u1d2e X\u1d2e<\/strong>, meaning she has <strong>two normal alleles<\/strong> and is not a carrier. The father is <strong>X\u1d47 Y<\/strong>, meaning he <strong>is color-blind<\/strong>.<\/p>\n\n\n\n<p>When we cross these genotypes in a Punnett square, the mother can only pass on the <strong>X\u1d2e allele<\/strong>, and the father can pass on either <strong>X\u1d47<\/strong> or <strong>Y<\/strong>. The resulting children will be:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>All daughters will be <strong>X\u1d2e X\u1d47<\/strong>: not color-blind, but <strong>carriers<\/strong>.<\/li>\n\n\n\n<li>All sons will be <strong>X\u1d2e Y<\/strong>: they inherit the X\u1d2e from their mother and Y from their father, so they will have <strong>normal vision<\/strong>.<\/li>\n<\/ul>\n\n\n\n<p>Since none of the daughters are <strong>X\u1d47 X\u1d47<\/strong>, <strong>no daughter<\/strong> will be color-blind. And none of the sons inherit the X\u1d47 allele from the mother (because she doesn&#8217;t have it), so <strong>no son<\/strong> will be color-blind either.<\/p>\n\n\n\n<p>Thus, the chance of having a color-blind daughter or son is <strong>0 out of 4<\/strong>, or <strong>0%<\/strong>.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img decoding=\"async\" src=\"https:\/\/learnexams.com\/blog\/wp-content\/uploads\/2025\/07\/learnexams-banner6-658.jpeg\" alt=\"\" class=\"wp-image-256638\"\/><\/figure>\n","protected":false},"excerpt":{"rendered":"<p>In humans, red-green color-blindness is controlled by a gene on the X chromosome. For females, normal color vision is dominant to color-blindness. A convenient way to represent the gene is to use an X (for the X chromosome) with a superscript for the particular allele. Thus, if we use the letter &#8220;B&#8221; for the normal [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"categories":[25],"tags":[],"class_list":["post-256637","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/256637","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/comments?post=256637"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/256637\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=256637"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=256637"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=256637"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}