{"id":222227,"date":"2025-05-31T07:04:08","date_gmt":"2025-05-31T07:04:08","guid":{"rendered":"https:\/\/learnexams.com\/blog\/?p=222227"},"modified":"2025-05-31T07:04:11","modified_gmt":"2025-05-31T07:04:11","slug":"this-pedigree-chart-shows-the-inheritance-of-sickle-cell-anemia-in-three-generations-of-a-family","status":"publish","type":"post","link":"https:\/\/www.learnexams.com\/blog\/2025\/05\/31\/this-pedigree-chart-shows-the-inheritance-of-sickle-cell-anemia-in-three-generations-of-a-family\/","title":{"rendered":"This pedigree chart shows the inheritance of sickle cell anemia in three generations of a family."},"content":{"rendered":"\n<p>This pedigree chart shows the inheritance of sickle cell anemia in three generations of a family. Each male is symbolized by a square and each female is symbolized by a circle. A person who has sickle cell anemia is symbolized by a dark square or circle. The couple labeled 1 and 2 had five children, including one daughter with sickle cell anemia (5). 7a. In the pedigree, write the genotypes of each person who is labeled with a number. 7b. If parents 3 and 4 had a fourth child, what is the probability that this child would have sickle cell anemia? 0% 25% 50% 75% 100% 7c. Explain your reasoning.<\/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<p>To answer this pedigree question about sickle cell anemia, we need to understand how this disorder is inherited.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">Background:<\/h3>\n\n\n\n<p>Sickle cell anemia is inherited in an <strong>autosomal recessive<\/strong> pattern. This means a person must inherit <strong>two copies of the sickle cell allele (s)<\/strong> \u2014 one from each parent \u2014 to have the disease (<strong>ss<\/strong>). A person with only one sickle cell allele (<strong>Ss<\/strong>) is a <strong>carrier<\/strong> and typically does not show symptoms.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">7a. <strong>Genotypes of each labeled person:<\/strong><\/h3>\n\n\n\n<p>Let\u2019s assume the pedigree chart provides the following:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>1 (Male)<\/strong>: Father of 5 children, one of whom has sickle cell anemia.<\/li>\n\n\n\n<li><strong>2 (Female)<\/strong>: Mother, also unaffected.<\/li>\n\n\n\n<li><strong>5 (Daughter)<\/strong>: Has sickle cell anemia.<\/li>\n\n\n\n<li><strong>3 and 4<\/strong>: A couple who are both children of 1 and 2, and are parents to three children.<\/li>\n<\/ul>\n\n\n\n<p>Now, based on this:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>1 and 2<\/strong>: Both must be <strong>Ss<\/strong>. Why? They have a child (<strong>5<\/strong>) with the disease, meaning both must have passed on an <strong>s<\/strong> allele.<\/li>\n\n\n\n<li><strong>5<\/strong>: Must be <strong>ss<\/strong> (has the disease).<\/li>\n\n\n\n<li><strong>3 and 4<\/strong>: Both are children of 1 and 2, so they each have a <strong>50%<\/strong> chance of inheriting <strong>s<\/strong> and <strong>50%<\/strong> chance of inheriting <strong>S<\/strong>. But because they have had children together, and assuming their children are unaffected, the most likely genotype is <strong>Ss<\/strong> for both (we\u2019ll assume this unless evidence says otherwise).<\/li>\n<\/ul>\n\n\n\n<p>So:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>1<\/strong>: Ss<\/li>\n\n\n\n<li><strong>2<\/strong>: Ss<\/li>\n\n\n\n<li><strong>3<\/strong>: Ss<\/li>\n\n\n\n<li><strong>4<\/strong>: Ss<\/li>\n\n\n\n<li><strong>5<\/strong>: ss<\/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\">7b. <strong>Probability that parents 3 and 4 will have a child with sickle cell anemia:<\/strong><\/h3>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><strong>Answer: 25%<\/strong><\/p>\n<\/blockquote>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">7c. <strong>Explanation<\/strong><\/h3>\n\n\n\n<p>Sickle cell anemia is a genetic condition caused by a mutation in the hemoglobin gene. It is inherited in an autosomal recessive manner, which means that a child must inherit two copies of the faulty gene\u2014one from each parent\u2014to be affected by the disease.<\/p>\n\n\n\n<p>In the pedigree, both parents labeled 3 and 4 are children of carriers (1 and 2), and therefore are most likely carriers themselves. Carriers have one normal allele (S) and one mutated allele (s), giving them the genotype <strong>Ss<\/strong>. Carriers do not typically show symptoms of sickle cell anemia but can pass the mutated allele to their children.<\/p>\n\n\n\n<p>When two carriers (Ss and Ss) have children, each child has a:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>25% chance of inheriting <strong>SS<\/strong> (not a carrier and not affected),<\/li>\n\n\n\n<li>50% chance of inheriting <strong>Ss<\/strong> (a carrier),<\/li>\n\n\n\n<li>25% chance of inheriting <strong>ss<\/strong> (affected by sickle cell anemia).<\/li>\n<\/ul>\n\n\n\n<p>These probabilities are derived from a simple Punnett square crossing Ss \u00d7 Ss:<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th><\/th><th>S (from one parent)<\/th><th>s (from one parent)<\/th><\/tr><\/thead><tbody><tr><td><strong>S<\/strong><\/td><td>SS<\/td><td>Ss<\/td><\/tr><tr><td><strong>s<\/strong><\/td><td>Ss<\/td><td>ss<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p>So, for every pregnancy, there is a <strong>25% chance<\/strong> the child will inherit both mutated alleles (ss) and have sickle cell anemia.<\/p>\n\n\n\n<p>Therefore, if parents 3 and 4 have a fourth child, there is a <strong>25% probability<\/strong> that the child will have sickle cell anemia, assuming both are carriers.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img decoding=\"async\" src=\"https:\/\/learnexams.com\/blog\/wp-content\/uploads\/2025\/05\/learnexams-banner4-181.jpeg\" alt=\"\" class=\"wp-image-222228\"\/><\/figure>\n","protected":false},"excerpt":{"rendered":"<p>This pedigree chart shows the inheritance of sickle cell anemia in three generations of a family. Each male is symbolized by a square and each female is symbolized by a circle. A person who has sickle cell anemia is symbolized by a dark square or circle. The couple labeled 1 and 2 had five children, [&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-222227","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/222227","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=222227"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/222227\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=222227"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=222227"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=222227"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}