{"id":256642,"date":"2025-07-16T11:49:08","date_gmt":"2025-07-16T11:49:08","guid":{"rendered":"https:\/\/learnexams.com\/blog\/?p=256642"},"modified":"2025-07-16T11:49:11","modified_gmt":"2025-07-16T11:49:11","slug":"red-green-color-blindness-is-caused-by-a-sex-linked-recessive-allele","status":"publish","type":"post","link":"https:\/\/www.learnexams.com\/blog\/2025\/07\/16\/red-green-color-blindness-is-caused-by-a-sex-linked-recessive-allele\/","title":{"rendered":"Red-green color blindness is caused by a sex-linked recessive allele."},"content":{"rendered":"\n
Red-green color blindness is caused by a sex-linked recessive allele. A color-blind man marries a woman with normal vision whose father was color blind. What is the probability that they will have a color-blind daughter? What is the probability that their first son will be color-blind? (Note the different wording in the two questions.)<\/p>\n\n\n\n
The Correct Answer and Explanation is:<\/mark><\/strong><\/p>\n\n\n\n
Correct Answer:<\/h3>\n\n\n\n
\n
Probability of having a color-blind daughter<\/strong>: 25 percent<\/strong><\/li>\n\n\n\n
Probability that their first son will be color-blind<\/strong>: 50 percent<\/strong><\/li>\n<\/ul>\n\n\n\n\n\n\n\n
Explanation:<\/h3>\n\n\n\n
Red-green color blindness is a sex-linked recessive trait<\/strong>, which means the gene responsible is located on the X chromosome<\/strong>. Males have XY<\/strong> sex chromosomes, and females have XX<\/strong>. Since males only have one X chromosome, if they inherit the allele for color blindness (represented as X\u1d47<\/strong>), they will express the trait. Females need two copies<\/strong> of the allele (X\u1d47X\u1d47) to be color blind; if they have only one (X\u1d2eX\u1d47), they are carriers but not affected.<\/p>\n\n\n\n
Step 1: Determine genotypes<\/h4>\n\n\n\n
\n
Color-blind man<\/strong>: X\u1d47Y<\/li>\n\n\n\n
Woman with normal vision but whose father was color-blind<\/strong>:\n
\n
Her father: X\u1d47Y (color-blind)<\/li>\n\n\n\n
Therefore, she must be a carrier<\/strong>: X\u1d2eX\u1d47<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n\n\n\n
50 percent chance to be carriers (X\u1d2eX\u1d47)<\/li>\n\n\n\n
50 percent chance to be color blind (X\u1d47X\u1d47)<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n\n\n\n
So, the chance of a daughter being color blind<\/strong> = 1 out of 4 total outcomes = 25 percent<\/strong><\/p>\n\n\n\n
\n
Sons<\/strong>:\n
\n
50 percent chance to be normal (X\u1d2eY)<\/li>\n\n\n\n
50 percent chance to be color blind (X\u1d47Y)<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n\n\n\n
So, the chance that the first son will be color blind<\/strong> = 50 percent<\/strong><\/p>\n\n\n\n
This difference arises because the daughter must inherit two X\u1d47 alleles<\/strong>, while the son only needs one.<\/p>\n\n\n\n<\/figure>\n","protected":false},"excerpt":{"rendered":"
Red-green color blindness is caused by a sex-linked recessive allele. A color-blind man marries a woman with normal vision whose father was color blind. What is the probability that they will have a color-blind daughter? What is the probability that their first son will be color-blind? (Note the different wording in the two questions.) The […]<\/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-256642","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/256642","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=256642"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/256642\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=256642"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=256642"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=256642"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
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<\/figure>\n","protected":false},"excerpt":{"rendered":"