The Structure of DNA DNA Has the Structure of a Winding Staircase Early 1950’s, James Watson and...
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![Page 1: The Structure of DNA DNA Has the Structure of a Winding Staircase Early 1950’s, James Watson and Francis Crick determined that DNA is a molecule that is.](https://reader036.fdocuments.net/reader036/viewer/2022083004/56649dd35503460f94aca79b/html5/thumbnails/1.jpg)
The Structure of DNADNA Has the Structure of a Winding
Staircase• Early 1950’s, James
Watson and Francis Crick determined that DNA is a molecule that is a double helix.
• A double helix is two strands twisted around each other.
![Page 2: The Structure of DNA DNA Has the Structure of a Winding Staircase Early 1950’s, James Watson and Francis Crick determined that DNA is a molecule that is.](https://reader036.fdocuments.net/reader036/viewer/2022083004/56649dd35503460f94aca79b/html5/thumbnails/2.jpg)
• Each strand is composed of nucleotides.
• Nucleotides are the subunits that make up DNA.
• Made of 3 parts: phosphate group, deoxyribose (sugar) & a nitrogen base.
![Page 3: The Structure of DNA DNA Has the Structure of a Winding Staircase Early 1950’s, James Watson and Francis Crick determined that DNA is a molecule that is.](https://reader036.fdocuments.net/reader036/viewer/2022083004/56649dd35503460f94aca79b/html5/thumbnails/3.jpg)
Nucleotide Components
1. Deoxyribose- The five carbon sugar in DNA. Forms the full name of DNA (deoxyribonucleic acid).
2. Phosphate Group- alternates with deoxyribose to form the sides of the “ladder”.
3. Nitrogen bases- Adenine (A), Thymine (T), Cytosine (C), & Guanine (G).
![Page 4: The Structure of DNA DNA Has the Structure of a Winding Staircase Early 1950’s, James Watson and Francis Crick determined that DNA is a molecule that is.](https://reader036.fdocuments.net/reader036/viewer/2022083004/56649dd35503460f94aca79b/html5/thumbnails/4.jpg)
Chargaff’s Observations
• In 1949, Erwin Chargaff’s data showed that for each organism he studied, the amount of adenine always equaled the amount of thymine.
• And, the amount of cytosine always equaled the amount of guanine.
![Page 5: The Structure of DNA DNA Has the Structure of a Winding Staircase Early 1950’s, James Watson and Francis Crick determined that DNA is a molecule that is.](https://reader036.fdocuments.net/reader036/viewer/2022083004/56649dd35503460f94aca79b/html5/thumbnails/5.jpg)
• In 1952, Watson & Crick determined the structure of DNA with the help of data collected by Rosalind Franklin and Chargaff.
DNA Model
![Page 6: The Structure of DNA DNA Has the Structure of a Winding Staircase Early 1950’s, James Watson and Francis Crick determined that DNA is a molecule that is.](https://reader036.fdocuments.net/reader036/viewer/2022083004/56649dd35503460f94aca79b/html5/thumbnails/6.jpg)
Base-Pairing Rules• Adenine forms 2
hydrogen bonds with Thymine
• Cytosine forms 3 hydrogen bonds with Guanine
• The hydrogen bonds between the nitrogen bases keep the two strands of DNA together.
• Each strand is complementary to the other. Ex. TCGAACT is complementary to AGCTTGA