[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"detail-sidebar-cat-0-en-105":3,"doc-seo-661047-105":59,"doc-detail-661047-en":129},{"code":4,"msg":5,"data":6},0,"success",[7,13,18,23,28,33,38,43,48,51,55],{"id":8,"doc_module":4,"doc_module_name":9,"category_name":10,"show_sort_weight":11,"slug":12},1,"Document","Story & Novel",90,"story-novel",{"id":14,"doc_module":4,"doc_module_name":9,"category_name":15,"show_sort_weight":16,"slug":17},2,"Literature",80,"literature",{"id":19,"doc_module":4,"doc_module_name":9,"category_name":20,"show_sort_weight":21,"slug":22},4,"Exam",70,"exam",{"id":24,"doc_module":4,"doc_module_name":9,"category_name":25,"show_sort_weight":26,"slug":27},5,"Comic",60,"comic",{"id":29,"doc_module":4,"doc_module_name":9,"category_name":30,"show_sort_weight":31,"slug":32},6,"Technology",50,"technology",{"id":34,"doc_module":4,"doc_module_name":9,"category_name":35,"show_sort_weight":36,"slug":37},7,"Healthcare",40,"healthcare",{"id":39,"doc_module":4,"doc_module_name":9,"category_name":40,"show_sort_weight":41,"slug":42},8,"Research & Report",30,"research-report",{"id":44,"doc_module":4,"doc_module_name":9,"category_name":45,"show_sort_weight":46,"slug":47},9,"Religion & Spirituality",20,"religion-spirituality",{"id":46,"doc_module":4,"doc_module_name":9,"category_name":49,"show_sort_weight":46,"slug":50},"World Cup","world-cup",{"id":52,"doc_module":4,"doc_module_name":9,"category_name":53,"show_sort_weight":52,"slug":54},10,"Lifestyle","lifestyle",{"id":56,"doc_module":4,"doc_module_name":9,"category_name":57,"show_sort_weight":24,"slug":58},19,"General","general",{"code":4,"msg":60,"data":61},"ok",{"site_id":62,"language":63,"slug":64,"title":65,"keywords":66,"description":67,"schema_data":68,"social_meta":122,"head_meta":124,"extra_data":126,"updated_unix":128},105,"en","structure-of-dna-the-double-helix-key-features-and-models","Structure of DNA (The Double Helix) - Key Features and Models","","DNA naturally exists as interacting chains forming a double-helix macromolecule proposed by Watson and Crick in 1953. Evidence from X-ray diffraction and chemical analysis supported base pairing rules: A pairs with T and G pairs with C via hydrogen bonding. The model describes antiparallel polynucleotide strands, sugar-phosphate backbone placement, groove formation, and helix dimensions. It further outlines B-, A-, and Z-DNA structural variants and their conditions, stability, and base-pair spacing.",{"@graph":69,"@context":121},[70,84,104],{"@type":71,"itemListElement":72},"BreadcrumbList",[73,77,79,82],{"item":74,"name":75,"@type":76,"position":8},"https://docshare.wps.com","Home","ListItem",{"item":78,"name":9,"@type":76,"position":14},"https://docshare.wps.com/document/",{"item":80,"name":35,"@type":76,"position":81},"https://docshare.wps.com/document/healthcare/",3,{"item":83,"name":65,"@type":76,"position":19},"https://docshare.wps.com/document/structure-of-dna-the-double-helix-key-features-and-models/661047/",{"url":83,"name":65,"@type":85,"image":86,"author":91,"headline":65,"publisher":94,"fileFormat":97,"inLanguage":63,"description":67,"dateModified":98,"datePublished":98,"encodingFormat":97,"isAccessibleForFree":99,"interactionStatistic":100},"DigitalDocument",{"url":87,"@type":88,"width":89,"height":90},"https://docshare.wps.com/thumbnails/structure-of-dna-the-double-helix-key-features-and-models/661047.png","ImageObject",300,407,{"name":92,"@type":93},"Taylor Morgan","Person",{"url":74,"name":95,"@type":96},"DocShare","Organization","application/pdf","2026-10-28",true,{"@type":101,"interactionType":102,"userInteractionCount":4},"InteractionCounter",{"@type":103},"ViewAction",{"@type":105,"mainEntity":106},"FAQPage",[107,113,117],{"name":108,"@type":109,"acceptedAnswer":110},"What evidence supported the Watson and Crick double-helix model of DNA?","Question",{"text":111,"@type":112},"X-ray diffraction patterns and chemical analysis supported the model. The analysis showed A pairs with T and G pairs with C, and this pairing aided alignment in the helix.","Answer",{"name":114,"@type":109,"acceptedAnswer":115},"How do hydrogen bonds determine DNA base alignment?",{"text":116,"@type":112},"Hydrogen bonds form between paired bases on opposite chains. There are two hydrogen bonds for A–T and three for G–C, helping hold the two strands together.",{"name":118,"@type":109,"acceptedAnswer":119},"What are the main differences among B-DNA, A-DNA, and Z-DNA?",{"text":120,"@type":112},"B-DNA occurs naturally under normal conditions with right-handed coils. A-DNA is the dehydrated, more compact form under decreased hydration and higher sodium ions, while Z-DNA is left-handed, forms in small cellular proportions, and is less stable, stabilized by high salt concentration.","https://schema.org",{"og:url":83,"og:type":123,"og:title":65,"og:site_name":95,"og:description":67},"article",{"robots":125,"canonical":83},"index,follow",{"doc_id":127,"site_id":62},661047,1793156738,{"code":4,"msg":5,"data":130},{"doc_id":127,"user_id":131,"nickname":92,"user_avatar":132,"doc_module":4,"category_id":34,"category_name":35,"doc_title":65,"doc_description":67,"doc_content":133,"file_id":134,"file_url":135,"file_type":136,"file_size":137,"view_count":4,"is_deleted":4,"is_public":8,"is_downloadable":8,"audit_status":8,"page_count":24,"language":138,"language_code":63,"site_id":62,"html_lang":63,"table_of_contents":139,"faqs":140,"seo_title":141,"seo_description":67,"update_tm":128,"read_time":142},1099523885336,"https://ap-avatar.wpscdn.com/davatar_276721f389ce27ea32af1340a28f341c","Structure of DNA (The Double Helix)  \nIt was suspected that most naturally occurring DNA did not exist as single chains. Instead two or more chains appear to interact with one another in some way. The resulting macromolecules were known to be long, thin and rigid such that they formed highly viscous solution in water. The double Helix structure of DNA was proposed by James Watson and Francis Crick in 1953 . It was based primarily on model building and X-ray diffraction pattern. Information from X-ray patterns was added to information from chemical analysis that showed that the amount of A was always same as the amount of T and that the amount of G always equal to the amount of C. Both of these lines of evidence were used to conclude that DNA consist of polynucleotide chains wrapped around eachother to form in helix . Hydrogen bonds between bases on opposite chains determine the alignment of helix. The paired bases lie in a planes perpendicular to the Helix . The sugar phosphate backbone in the outer part of the Helix . The chains run in antiparallel directions one 3’to 5’ and other 5’to3’. Important features of the Watson and Crick model are :  \n1.The base pairing is complementary, meaning that adenine pairs with thymine and guanine pairs with cytosine . This complementary base pairing occurs along entire double Helix, the two chains are also referred as complimentary chains. And adenine-thymine(A-T) base pair has to hydrogen bonds between them whereas a guanosine-cytosine(G-C) pair has three.  \n2.The inside diameter of sugar phosphate backbone of the double Helix is about 1.1 nm. The distance between the points of attachment of the bases ofthe 2 strands ofthe sugar phosphate backbone is the same for two base pairs(A-T and G-C),about 1.1 nm. This gives DNA an extremely ordered structure.  \n3.The outside diameter of the Helix is 20 Ao(2nm) . The length of one complete turn of the helix along its axis is 34Ao(3.4nm) and contains ten base pairs.  \n4.The double Helix has empty spaces known as grooves. There is a major groove and a smaller minor groove in the double helix. Both can be sites at which drugs or polypeptides bind to DNA.  \nImportant features of Watson and Cricks model:  \n1. The double Helix comprises of two complementary polynucleotide chains .  \n2. The two polynucleotide chains are wrapped clockwise around central access to form circular staircase type structure .  \n3. The two strands of double Helix are antiparallel i.e., they run in opposite direction one chain is aligned in 5’→ 3′direction and the other chain is aligned in 3’→ 5′ direction.  \n4. Each polynucleotide chain has sugar phosphate backbone and nitrogenous bases are directed inside the Helix i.e., towards the central axis .the sugar phosphate backbone is formed of covalently bonded deoxyribose and phosphate groups and therefore, occur on the outside of Helix.  \n5. The phosphate groups give the molecule negative charge  \n6. The nitrogenous bases are hydrophobic in nature. They avoid water and therefore remain inside the Helix.  \n7. The diameter of double Helix is 2nm.  \n8. The nitrogenous bases lie almost perpendicular to the axis of molecule. Therefore these are stacked one on top of another. The hydrophobic interaction between the bases provide stability to DNA.  \n9. The nitrogenous bases of two antiparallel polynucleotide strands are linked through hydrogen bonds. there are two hydrogen bonds between adenine and thymine and three between guanine and cytosine .The hydrogen bonds are the only attractive forces between two polynucleotide chains ofthe double Helix these serve to hold the strands together .  \n10. There are ten base pairs in one turn Helix therefore each turn of the Helix is 3.4nm.  \n11. The double Helix has two helical groups a major groove which is deep and wide and minor groove which is shallow and narrow.  \n\\# The double helical structure described by Watson and Crick was also B-DNA. The other secondary structures can occur depending on th","cbCaieULGdh58JpJ","https://ap.wps.com/l/cbCaieULGdh58JpJ","pdf",415038,"English","# Structure of DNA (The Double Helix)\n## Watson and Crick model and base pairing\n## Helix geometry and grooves\n## Additional key features of the model\n## B-DNA, A-DNA, and Z-DNA forms\n# Denaturation and Renaturation of DNA","[{\"question\":\"What evidence supported the Watson and Crick double-helix model of DNA?\",\"answer\":\"X-ray diffraction patterns and chemical analysis supported the model. The analysis showed A pairs with T and G pairs with C, and this pairing aided alignment in the helix.\"},{\"question\":\"How do hydrogen bonds determine DNA base alignment?\",\"answer\":\"Hydrogen bonds form between paired bases on opposite chains. There are two hydrogen bonds for A–T and three for G–C, helping hold the two strands together.\"},{\"question\":\"What are the main differences among B-DNA, A-DNA, and Z-DNA?\",\"answer\":\"B-DNA occurs naturally under normal conditions with right-handed coils. A-DNA is the dehydrated, more compact form under decreased hydration and higher sodium ions, while Z-DNA is left-handed, forms in small cellular proportions, and is less stable, stabilized by high salt concentration.\"}]","Structure of DNA (The Double Helix) - Key Features and Models | PDF",13]