{"id":247393,"date":"2025-07-07T17:00:55","date_gmt":"2025-07-07T17:00:55","guid":{"rendered":"https:\/\/learnexams.com\/blog\/?p=247393"},"modified":"2025-07-07T17:00:57","modified_gmt":"2025-07-07T17:00:57","slug":"during-the-s-phase-a-part-of-interphase-the-dna-is-replicated","status":"publish","type":"post","link":"https:\/\/www.learnexams.com\/blog\/2025\/07\/07\/during-the-s-phase-a-part-of-interphase-the-dna-is-replicated\/","title":{"rendered":"During the S phase (a part of interphase) the DNA is replicated."},"content":{"rendered":"\n

During the S phase (a part of interphase) the DNA is replicated. We will learn about DNA replication in a later chapter. For now you need to know that each of the 46 individual chromosomes that existed in the human cell are copied and the copy becomes attached to the original chromosome at the centromere (centromeric region) of the chromosome. Whenever you see a drawing of chromosomes that looks like a long \u201cX\u201d shape (see figure 10.7 for an example) you are seeing ONE chromosome with is exact copy attached. This chromosome with its copy attached is called a pair of _<\/em><\/strong> ________<\/em><\/strong><\/em><\/strong> . How many pairs of sister chromatids would you find in a human cell right after S-phase has completed? _<\/strong> Draw a pair of sister chromatids and label the centromere, kinetochore, and mitotic spindle.<\/p>\n\n\n\n

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

The correct answer is: sister chromatids<\/strong> Number of pairs of sister chromatids after S-phase: 46<\/strong><\/p>\n\n\n\n

During the S phase of interphase, the cell undergoes DNA replication to prepare for cell division. Each of the 46 chromosomes in a human somatic cell is duplicated, resulting in two identical copies of each chromosome. These identical copies are called sister chromatids. They remain physically connected at a region known as the centromere.<\/p>\n\n\n\n

A pair of sister chromatids is still considered one chromosome because they carry identical genetic information and are joined together. The X-shaped structure often seen in diagrams represents this duplicated chromosome, with each arm of the X being one chromatid. The centromere is the constricted region where the two chromatids are held together. Attached to the centromere is a protein structure called the kinetochore. The kinetochore serves as the attachment point for spindle fibers, which are part of the mitotic spindle apparatus.<\/p>\n\n\n\n

The mitotic spindle is a structure made of microtubules that orchestrates the movement of chromosomes during cell division. It ensures that each daughter cell receives an identical set of chromosomes. During mitosis, the spindle fibers attach to the kinetochores and pull the sister chromatids apart toward opposite poles of the cell. Once separated, each chromatid becomes an individual chromosome in the daughter cells.<\/p>\n\n\n\n

Immediately after the S phase, a human cell contains 46 chromosomes, each consisting of two sister chromatids. Therefore, there are 46 pairs of sister chromatids, totaling 92 chromatids. This duplication is crucial for maintaining genetic continuity across cell generations.<\/p>\n\n\n\n

\"Draw<\/figure>\n\n\n\n
\"\"<\/figure>\n","protected":false},"excerpt":{"rendered":"

During the S phase (a part of interphase) the DNA is replicated. We will learn about DNA replication in a later chapter. For now you need to know that each of the 46 individual chromosomes that existed in the human cell are copied and the copy becomes attached to the original chromosome at the centromere […]<\/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-247393","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/247393","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=247393"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/247393\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=247393"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=247393"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=247393"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}