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The Universal Structure of DNA: Insights into its Composition and Double Helix Formation

DNA, found in all organisms, is composed of four types of nucleotides, each consisting of a phosphate group, a deoxyribose sugar, and a nitrogen-containing base. The only variation among these nucleotides lies in their bases. Watson and Crick revealed DNA's double helix structure, supported by Rosalind Franklin's X-ray images and Erwin Chargaff's base-pairing rules, which state that Adenine pairs with Thymine and Cytosine pairs with Guanine. The DNA backbone is formed by covalent bonds, while the bases are held together by hydrogen bonds.

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The Universal Structure of DNA: Insights into its Composition and Double Helix Formation

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  1. KEY CONCEPT DNA structure is the same in all organisms.

  2. phosphate group nitrogen-containing base deoxyribose (sugar) DNA is composed of four types of nucleotides. • DNA is made up of a long chain of nucleotides. • Each nucleotide has three parts. • a phosphate group • a deoxyribose sugar • a nitrogen-containing base

  3. The nitrogen containing bases are the only difference in the four nucleotides.

  4. Watson and Crick determined the three-dimensional structure of DNA by building models. • They realized that DNA is a double helix that is made up of a sugar-phosphate backbone on the outside with bases on the inside.

  5. Watson and Crick’s discovery built on the work of Rosalind Franklin and Erwin Chargaff. • Franklin’s x-ray images suggested that DNA was a double helix of even width. • Chargaff’s rules stated that A=T and C=G.

  6. G C A T Nucleotides always pair in the same way. • The base-pairing rules show how nucleotides always pair up in DNA. • A pairs with T • C pairs with G • Because a pyrimidine (single ring) pairs with a purine (double ring), the helix has a uniform width.

  7. covalent bond hydrogen bond • The backbone is connected by covalent bonds. • The bases are connected by hydrogen bonds.

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