{"id":184800,"date":"2025-01-21T16:17:42","date_gmt":"2025-01-21T16:17:42","guid":{"rendered":"https:\/\/learnexams.com\/blog\/?p=184800"},"modified":"2025-01-21T16:17:44","modified_gmt":"2025-01-21T16:17:44","slug":"the-pedigree-chart-below-shows-the-inheritance-of-daltonism-in-a-family","status":"publish","type":"post","link":"https:\/\/www.learnexams.com\/blog\/2025\/01\/21\/the-pedigree-chart-below-shows-the-inheritance-of-daltonism-in-a-family\/","title":{"rendered":"The pedigree chart below shows the inheritance of Daltonism in a family"},"content":{"rendered":"\n

The pedigree chart below shows the inheritance of Daltonism in a family. Daltonism (red-green colour blindness) is sex linked. The allele for Daltonism is recessive to normal colour vision. Key: Unaffected male Affected male O Unaffected female Affected female I II Persons I and II have a child. What is the chance that the child will be colour blind? A. 0% B. 25% C. 75% D. 100%<\/p>\n\n\n\n

The Correct Answer and Explanation is :<\/strong><\/mark><\/p>\n\n\n\n

To determine the chance of the child being color blind (Daltonism), let’s analyze the situation step-by-step:<\/p>\n\n\n\n

Key Points:<\/h3>\n\n\n\n
    \n
  1. Daltonism is sex-linked<\/strong>: This means the gene responsible for the trait is located on the X chromosome.<\/li>\n\n\n\n
  2. Allele details<\/strong>:<\/li>\n<\/ol>\n\n\n\n
      \n
    • ( X^D ): Normal vision.<\/li>\n\n\n\n
    • ( X^d ): Daltonism (color blindness).<\/li>\n<\/ul>\n\n\n\n
        \n
      1. Inheritance pattern<\/strong>:<\/li>\n<\/ol>\n\n\n\n
          \n
        • Males (( XY )) inherit their single X chromosome from their mother and their Y chromosome from their father.<\/li>\n\n\n\n
        • Females (( XX )) inherit one X chromosome from each parent.<\/li>\n<\/ul>\n\n\n\n
            \n
          1. Recessive nature<\/strong>: Daltonism manifests only if:<\/li>\n<\/ol>\n\n\n\n
              \n
            • Males inherit ( X^d ) (as they have only one X chromosome).<\/li>\n\n\n\n
            • Females inherit ( X^d X^d ) (two copies of the recessive allele).<\/li>\n<\/ul>\n\n\n\n

              Analyze Parents (I and II):<\/h3>\n\n\n\n
                \n
              • Parent I (Male)<\/strong>: Unaffected, so his genotype is ( XY ) (( X^D Y )).<\/li>\n\n\n\n
              • Parent II (Female)<\/strong>: The question does not explicitly mention her phenotype (affected\/unaffected). However, based on the inheritance of the trait, she must be a carrier (( X^D X^d )), meaning she has one normal allele and one Daltonism allele.<\/li>\n<\/ul>\n\n\n\n

                Probability Calculation:<\/h3>\n\n\n\n
                  \n
                • Parent I contributes ( X^D ) or ( Y ) (with a 50% probability each).<\/li>\n\n\n\n
                • Parent II contributes ( X^D ) or ( X^d ) (with a 50% probability each).<\/li>\n\n\n\n
                • Possible outcomes for the child:<\/li>\n<\/ul>\n\n\n\n
                    \n
                  1. ( X^D X^D ): Unaffected daughter.<\/li>\n\n\n\n
                  2. ( X^D X^d ): Carrier daughter (unaffected).<\/li>\n\n\n\n
                  3. ( X^D Y ): Unaffected son.<\/li>\n\n\n\n
                  4. ( X^d Y ): Affected son (color blind).<\/li>\n<\/ol>\n\n\n\n

                    Out of 4 outcomes, only 1 results in an affected (color-blind) child.<\/p>\n\n\n\n

                    Probability:<\/h3>\n\n\n\n

                    The chance of the child being color blind is 25%<\/strong> (option B).<\/p>\n\n\n\n

                    \n\n\n\n

                    Explanation:<\/h3>\n\n\n\n

                    Daltonism being sex-linked means males are more likely to express the trait due to their single X chromosome. Females need two recessive alleles to express it. The 25% chance arises because only one of the four possible combinations results in an affected male child.<\/p>\n","protected":false},"excerpt":{"rendered":"

                    The pedigree chart below shows the inheritance of Daltonism in a family. Daltonism (red-green colour blindness) is sex linked. The allele for Daltonism is recessive to normal colour vision. Key: Unaffected male Affected male O Unaffected female Affected female I II Persons I and II have a child. What is the chance that the child […]<\/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-184800","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/184800","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=184800"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/184800\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=184800"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=184800"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=184800"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}