{"id":2523,"date":"2016-06-02T17:13:30","date_gmt":"2016-06-02T17:13:30","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/biologyxwaymakerxmaster\/?post_type=chapter&#038;p=2523"},"modified":"2024-04-26T00:36:33","modified_gmt":"2024-04-26T00:36:33","slug":"reading-structure-of-dna","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/wm-nmbiology1\/chapter\/reading-structure-of-dna\/","title":{"raw":"Structure of DNA","rendered":"Structure of DNA"},"content":{"raw":"<div class=\"textbox learning-objectives\">\r\n<h3>Learning Outcomes<\/h3>\r\n<ul>\r\n \t<li>Diagram the structure of DNA<\/li>\r\n<\/ul>\r\n<\/div>\r\nThe building blocks of DNA are <strong>nucleotides<\/strong>. The important components of each\u00a0nucleotide are a <span style=\"text-decoration: underline;\">nitrogenous base<\/span>, <span style=\"text-decoration: underline;\">deoxyribose (5-carbon sugar<\/span>), and a <span style=\"text-decoration: underline;\">phosphate<\/span> group (see Figure\u00a01). Each\u00a0nucleotide is named depending on its\u00a0nitrogenous base. The nitrogenous base can be a <strong>purine<\/strong>, such as adenine (A) and guanine (G), or a <strong>pyrimidine<\/strong>, such as cytosine (C) and thymine (T). Uracil (U) is also a pyrimidine (as seen in Figure\u00a01), but it only occurs in RNA, which we will talk more about later.\r\n\r\n[caption id=\"attachment_6617\" align=\"aligncenter\" width=\"1024\"]<a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/2318\/2016\/06\/28161243\/Nucleic-Acid-Structure1.jpg\"><img class=\"wp-image-6617 size-large\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/2318\/2016\/06\/28161243\/Nucleic-Acid-Structure1-1024x456.jpg\" alt=\"Illustration depicts the structure of a nucleoside, which is made up of a pentose with a nitrogenous base attached at the 1' position. There are two kinds of nitrogenous bases: pyrimidines, which have one six-membered ring, and purines, which have a six-membered ring fused to a five-membered ring. Cytosine, thymine, and uracil are pyrimidines, and adenine and guanine are purines. A nucleoside with a phosphate attached at the 5' position is called a mononucleotide. A nucleoside with two or three phosphates attached is called a nucleotide diphosphate or nucleotide triphosphate, respectively.\" width=\"1024\" height=\"456\" \/><\/a> Figure\u00a01. Each nucleotide is made up of a sugar, a phosphate group, and a nitrogenous base. The sugar is deoxyribose in DNA and ribose in RNA[\/caption]\r\n\r\nThe nucleotides combine with each other by covalent bonds known as <strong>phosphodiester bonds<\/strong> or linkages. \u00a0The phosphate residue is attached to the hydroxyl group of the 5\u2032 carbon of one sugar of one nucleotide and the hydroxyl group of the 3\u2032 carbon of the sugar of the next nucleotide, thereby forming a 5\u2032-3\u2032 phosphodiester bond.\r\n\r\nIn the 1950s, Francis <strong>Crick<\/strong> and James <strong>Watson<\/strong> worked together to determine the structure of DNA at the University of Cambridge, England. Other scientists like Linus Pauling and Maurice Wilkins were also actively exploring this field. Pauling had discovered the secondary structure of proteins using X-ray crystallography. In Wilkins' lab, researcher Rosalind Franklin was using X-ray diffraction methods to understand the structure of DNA. Watson and Crick were able to piece together the puzzle of the DNA molecule on the basis of Franklin's data because Crick had also studied X-ray diffraction (Figure\u00a02). In 1962, James Watson, Francis Crick, and Maurice Wilkins were awarded the Nobel Prize in Medicine. Unfortunately, by then Franklin had died, and Nobel prizes are not awarded posthumously.\r\n\r\n[caption id=\"attachment_1421\" align=\"aligncenter\" width=\"944\"]<img class=\"size-full wp-image-1421\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/110\/2016\/05\/02183446\/Figure_14_02_02ab_new.jpg\" alt=\"The photo in part A shows James Watson, Francis Crick, and Maclyn McCarty. The x-ray diffraction pattern in part b is symmetrical, with dots in an x-shape\" width=\"944\" height=\"476\" \/> Figure\u00a02. The work of pioneering scientists (a) James Watson, Francis Crick, and Maclyn McCarty led to our present day understanding of DNA. Scientist Rosalind Franklin discovered (b) the X-ray diffraction pattern of DNA, which helped to elucidate its double helix structure. (credit a: modification of work by Marjorie McCarty, Public Library of Science)[\/caption]\r\n\r\nWatson and Crick proposed that DNA is made up of <em>two strands<\/em> that are twisted around each other to form a right-handed <em>helix<\/em>. <em>Base pairing<\/em> takes place between a purine and pyrimidine; namely, <em>A pairs with T and G pairs with C<\/em>. Adenine and thymine are complementary base pairs, and cytosine and guanine are also complementary base pairs. The base pairs are stabilized by <em>hydrogen bonds<\/em>; adenine and thymine form two hydrogen bonds and cytosine and guanine form three hydrogen bonds. The two strands are <em>anti-paralle<\/em>l in nature; that is, the 3\u2032 end of one strand faces the 5\u2032 end of the other strand. The sugar and phosphate of the nucleotides form the backbone of the structure, whereas the nitrogenous bases are stacked inside. Each base pair is separated from the other base pair by a distance of 0.34 nm, and each turn of the helix measures 3.4 nm. Therefore, ten base pairs are present per turn of the helix. The diameter of the DNA double helix is 2 nm, and it is uniform throughout. Only the pairing between a purine and pyrimidine can explain the uniform diameter. The twisting of the two strands around each other results in the formation of uniformly spaced major and minor grooves (Figure\u00a03).\r\n\r\n[caption id=\"attachment_1422\" align=\"aligncenter\" width=\"1024\"]<img class=\"size-large wp-image-1422\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/110\/2016\/05\/02183514\/Figure_14_02_03abc-1024x353.jpg\" alt=\"Part A shows an illustration of a DNA double helix, which has a sugar-phosphate backbone on the outside and nitrogenous base pairs on the inside. Part B shows base pairing between thymine and adenine, which form two hydrogen bonds, and between guanine and cytosine, which form three hydrogen bonds. Part C shows a molecular model of the DNA double helix. The outside of the helix alternates between wide gaps, called major grooves, and narrow gaps, called minor grooves.\" width=\"1024\" height=\"353\" \/> Figure\u00a03. DNA has (a) a double helix structure and (b) phosphodiester bonds. The (c) major and minor grooves are binding sites for DNA binding proteins during processes such as transcription (the copying of RNA from DNA) and replication.[\/caption]\r\n\r\n<div class=\"textbox tryit\">\r\n<h3>Try It<\/h3>\r\nhttps:\/\/assess.lumenlearning.com\/practice\/07f62dcd-d583-45ad-b2e4-419b0a04f435\r\n<\/div>","rendered":"<div class=\"textbox learning-objectives\">\n<h3>Learning Outcomes<\/h3>\n<ul>\n<li>Diagram the structure of DNA<\/li>\n<\/ul>\n<\/div>\n<p>The building blocks of DNA are <strong>nucleotides<\/strong>. The important components of each\u00a0nucleotide are a <span style=\"text-decoration: underline;\">nitrogenous base<\/span>, <span style=\"text-decoration: underline;\">deoxyribose (5-carbon sugar<\/span>), and a <span style=\"text-decoration: underline;\">phosphate<\/span> group (see Figure\u00a01). Each\u00a0nucleotide is named depending on its\u00a0nitrogenous base. The nitrogenous base can be a <strong>purine<\/strong>, such as adenine (A) and guanine (G), or a <strong>pyrimidine<\/strong>, such as cytosine (C) and thymine (T). Uracil (U) is also a pyrimidine (as seen in Figure\u00a01), but it only occurs in RNA, which we will talk more about later.<\/p>\n<div id=\"attachment_6617\" style=\"width: 1034px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/2318\/2016\/06\/28161243\/Nucleic-Acid-Structure1.jpg\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-6617\" class=\"wp-image-6617 size-large\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/2318\/2016\/06\/28161243\/Nucleic-Acid-Structure1-1024x456.jpg\" alt=\"Illustration depicts the structure of a nucleoside, which is made up of a pentose with a nitrogenous base attached at the 1' position. There are two kinds of nitrogenous bases: pyrimidines, which have one six-membered ring, and purines, which have a six-membered ring fused to a five-membered ring. Cytosine, thymine, and uracil are pyrimidines, and adenine and guanine are purines. A nucleoside with a phosphate attached at the 5' position is called a mononucleotide. A nucleoside with two or three phosphates attached is called a nucleotide diphosphate or nucleotide triphosphate, respectively.\" width=\"1024\" height=\"456\" \/><\/a><\/p>\n<p id=\"caption-attachment-6617\" class=\"wp-caption-text\">Figure\u00a01. Each nucleotide is made up of a sugar, a phosphate group, and a nitrogenous base. The sugar is deoxyribose in DNA and ribose in RNA<\/p>\n<\/div>\n<p>The nucleotides combine with each other by covalent bonds known as <strong>phosphodiester bonds<\/strong> or linkages. \u00a0The phosphate residue is attached to the hydroxyl group of the 5\u2032 carbon of one sugar of one nucleotide and the hydroxyl group of the 3\u2032 carbon of the sugar of the next nucleotide, thereby forming a 5\u2032-3\u2032 phosphodiester bond.<\/p>\n<p>In the 1950s, Francis <strong>Crick<\/strong> and James <strong>Watson<\/strong> worked together to determine the structure of DNA at the University of Cambridge, England. Other scientists like Linus Pauling and Maurice Wilkins were also actively exploring this field. Pauling had discovered the secondary structure of proteins using X-ray crystallography. In Wilkins&#8217; lab, researcher Rosalind Franklin was using X-ray diffraction methods to understand the structure of DNA. Watson and Crick were able to piece together the puzzle of the DNA molecule on the basis of Franklin&#8217;s data because Crick had also studied X-ray diffraction (Figure\u00a02). In 1962, James Watson, Francis Crick, and Maurice Wilkins were awarded the Nobel Prize in Medicine. Unfortunately, by then Franklin had died, and Nobel prizes are not awarded posthumously.<\/p>\n<div id=\"attachment_1421\" style=\"width: 954px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-1421\" class=\"size-full wp-image-1421\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/110\/2016\/05\/02183446\/Figure_14_02_02ab_new.jpg\" alt=\"The photo in part A shows James Watson, Francis Crick, and Maclyn McCarty. The x-ray diffraction pattern in part b is symmetrical, with dots in an x-shape\" width=\"944\" height=\"476\" \/><\/p>\n<p id=\"caption-attachment-1421\" class=\"wp-caption-text\">Figure\u00a02. The work of pioneering scientists (a) James Watson, Francis Crick, and Maclyn McCarty led to our present day understanding of DNA. Scientist Rosalind Franklin discovered (b) the X-ray diffraction pattern of DNA, which helped to elucidate its double helix structure. (credit a: modification of work by Marjorie McCarty, Public Library of Science)<\/p>\n<\/div>\n<p>Watson and Crick proposed that DNA is made up of <em>two strands<\/em> that are twisted around each other to form a right-handed <em>helix<\/em>. <em>Base pairing<\/em> takes place between a purine and pyrimidine; namely, <em>A pairs with T and G pairs with C<\/em>. Adenine and thymine are complementary base pairs, and cytosine and guanine are also complementary base pairs. The base pairs are stabilized by <em>hydrogen bonds<\/em>; adenine and thymine form two hydrogen bonds and cytosine and guanine form three hydrogen bonds. The two strands are <em>anti-paralle<\/em>l in nature; that is, the 3\u2032 end of one strand faces the 5\u2032 end of the other strand. The sugar and phosphate of the nucleotides form the backbone of the structure, whereas the nitrogenous bases are stacked inside. Each base pair is separated from the other base pair by a distance of 0.34 nm, and each turn of the helix measures 3.4 nm. Therefore, ten base pairs are present per turn of the helix. The diameter of the DNA double helix is 2 nm, and it is uniform throughout. Only the pairing between a purine and pyrimidine can explain the uniform diameter. The twisting of the two strands around each other results in the formation of uniformly spaced major and minor grooves (Figure\u00a03).<\/p>\n<div id=\"attachment_1422\" style=\"width: 1034px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-1422\" class=\"size-large wp-image-1422\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/110\/2016\/05\/02183514\/Figure_14_02_03abc-1024x353.jpg\" alt=\"Part A shows an illustration of a DNA double helix, which has a sugar-phosphate backbone on the outside and nitrogenous base pairs on the inside. Part B shows base pairing between thymine and adenine, which form two hydrogen bonds, and between guanine and cytosine, which form three hydrogen bonds. Part C shows a molecular model of the DNA double helix. The outside of the helix alternates between wide gaps, called major grooves, and narrow gaps, called minor grooves.\" width=\"1024\" height=\"353\" \/><\/p>\n<p id=\"caption-attachment-1422\" class=\"wp-caption-text\">Figure\u00a03. DNA has (a) a double helix structure and (b) phosphodiester bonds. The (c) major and minor grooves are binding sites for DNA binding proteins during processes such as transcription (the copying of RNA from DNA) and replication.<\/p>\n<\/div>\n<div class=\"textbox tryit\">\n<h3>Try It<\/h3>\n<p>\t<iframe id=\"assessment_practice_07f62dcd-d583-45ad-b2e4-419b0a04f435\" class=\"resizable\" src=\"https:\/\/assess.lumenlearning.com\/practice\/07f62dcd-d583-45ad-b2e4-419b0a04f435?iframe_resize_id=assessment_practice_id_07f62dcd-d583-45ad-b2e4-419b0a04f435\" frameborder=\"0\" style=\"border:none;width:100%;height:100%;min-height:300px;\"><br \/>\n\t<\/iframe>\n<\/div>\n\n\t\t\t <section class=\"citations-section\" role=\"contentinfo\">\n\t\t\t <h3>Candela Citations<\/h3>\n\t\t\t\t\t <div>\n\t\t\t\t\t\t <div id=\"citation-list-2523\">\n\t\t\t\t\t\t\t <div class=\"licensing\"><div class=\"license-attribution-dropdown-subheading\">CC licensed content, Original<\/div><ul class=\"citation-list\"><li>Nucleic Acid Structure (a derivative from the original work). <strong>Authored by<\/strong>: Stephen Snyder. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY: Attribution<\/a><\/em><\/li><\/ul><div class=\"license-attribution-dropdown-subheading\">CC licensed content, Shared previously<\/div><ul class=\"citation-list\"><li>Biology. <strong>Provided by<\/strong>: OpenStaxCNX. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"http:\/\/cnx.org\/contents\/185cbf87-c72e-48f5-b51e-f14f21b5eabd@10.8\">http:\/\/cnx.org\/contents\/185cbf87-c72e-48f5-b51e-f14f21b5eabd@10.8<\/a>. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY: Attribution<\/a><\/em>. <strong>License Terms<\/strong>: Download for free at http:\/\/cnx.org\/contents\/185cbf87-c72e-48f5-b51e-f14f21b5eabd@10.8<\/li><li>Biology for AP Courses. <strong>Provided by<\/strong>: OpenStaxCNX. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"https:\/\/openstax.org\/books\/biology-ap-courses\/pages\/1-introduction\">https:\/\/openstax.org\/books\/biology-ap-courses\/pages\/1-introduction<\/a>. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY: Attribution<\/a><\/em>. <strong>License Terms<\/strong>: Download for free at https:\/\/openstax.org\/details\/books\/biology-ap-courses<\/li><\/ul><\/div>\n\t\t\t\t\t\t <\/div>\n\t\t\t\t\t <\/div>\n\t\t\t <\/section>","protected":false},"author":17,"menu_order":3,"template":"","meta":{"_candela_citation":"[{\"type\":\"cc\",\"description\":\"Biology\",\"author\":\"\",\"organization\":\"OpenStaxCNX\",\"url\":\"http:\/\/cnx.org\/contents\/185cbf87-c72e-48f5-b51e-f14f21b5eabd@10.8\",\"project\":\"\",\"license\":\"cc-by\",\"license_terms\":\"Download for free at http:\/\/cnx.org\/contents\/185cbf87-c72e-48f5-b51e-f14f21b5eabd@10.8\"},{\"type\":\"original\",\"description\":\"Nucleic Acid Structure (a derivative from the original work)\",\"author\":\"Stephen Snyder\",\"organization\":\"\",\"url\":\"\",\"project\":\"\",\"license\":\"cc-by\",\"license_terms\":\"\"},{\"type\":\"cc\",\"description\":\"Biology for AP Courses\",\"author\":\"\",\"organization\":\"OpenStaxCNX\",\"url\":\"https:\/\/openstax.org\/books\/biology-ap-courses\/pages\/1-introduction\",\"project\":\"\",\"license\":\"cc-by\",\"license_terms\":\"Download for free at https:\/\/openstax.org\/details\/books\/biology-ap-courses\"}]","CANDELA_OUTCOMES_GUID":"701d2031-564c-4377-b513-9e7ce5e7b142, 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