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Questions and Answers
What is the angle between adjacent residues in the same chain according to the text?
What is the angle between adjacent residues in the same chain according to the text?
What is the distance of a phosphorus atom from the fiber axis according to the text?
What is the distance of a phosphorus atom from the fiber axis according to the text?
What is the structural feature of the DNA that allows cations easy access to the phosphates?
What is the structural feature of the DNA that allows cations easy access to the phosphates?
What is the novel feature of the DNA structure?
What is the novel feature of the DNA structure?
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Which of the following is not mentioned in the text as contributing to the understanding of the DNA structure?
Which of the following is not mentioned in the text as contributing to the understanding of the DNA structure?
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What is the purpose of the fellowship from the National Foundation for Infantile Paralysis mentioned in the text?
What is the purpose of the fellowship from the National Foundation for Infantile Paralysis mentioned in the text?
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Which bases form a pair in the A Structure for Deoxyribose Nucleic Acid according to the text?
Which bases form a pair in the A Structure for Deoxyribose Nucleic Acid according to the text?
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Which hydrogen bonds connect purine position 6 to pyrimidine position 6 in the DNA structure?
Which hydrogen bonds connect purine position 6 to pyrimidine position 6 in the DNA structure?
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What is the significance of considering tautomeric forms in the A Structure for Deoxyribose Nucleic Acid?
What is the significance of considering tautomeric forms in the A Structure for Deoxyribose Nucleic Acid?
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Which bases have novel features and are of considerable biological interest?
Which bases have novel features and are of considerable biological interest?
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How many inter-twined chains are present in the model proposed by Pauling and Corey for nucleic acid structure?
How many inter-twined chains are present in the model proposed by Pauling and Corey for nucleic acid structure?
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What happens if an adenine forms one member of a pair according to the text?
What happens if an adenine forms one member of a pair according to the text?
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What is the significance of the ratio of adenine to thymine and guanine to cytosine being close to unity for deoxyribose nucleic acid?
What is the significance of the ratio of adenine to thymine and guanine to cytosine being close to unity for deoxyribose nucleic acid?
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What is the significance of the van der Waals distances appearing too small in the proposed structure?
What is the significance of the van der Waals distances appearing too small in the proposed structure?
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Why is it considered unlikely to build the proposed structure with a ribose sugar instead of deoxyribose?
Why is it considered unlikely to build the proposed structure with a ribose sugar instead of deoxyribose?
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What is the significance of the negatively charged phosphates near the axis of the proposed structure?
What is the significance of the negatively charged phosphates near the axis of the proposed structure?
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What is the significance of the material that gives the X-ray diagrams being the salt, not the free acid?
What is the significance of the material that gives the X-ray diagrams being the salt, not the free acid?
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What is the authors' overall assessment of the proposed structure for deoxyribose nucleic acid?
What is the authors' overall assessment of the proposed structure for deoxyribose nucleic acid?
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Study Notes
Angle and Distance in DNA Structure
- The angle between adjacent residues in the same chain is approximately 36 degrees.
- The distance of a phosphorus atom from the fiber axis is about 6.6 angstroms.
Structural Features Allowing Cation Access
- The structural feature of DNA facilitating cation access to phosphates is the overall negative charge on the phosphate groups.
Novel Features of DNA Structure
- A novel feature of DNA structure is its double helical arrangement, which enhances stability and functionality.
Contributions to Understanding DNA Structure
- The text does not mention historical models like the hypochromicity effect as contributing factors to the understanding of DNA structure.
Purpose of Fellowship
- The fellowship from the National Foundation for Infantile Paralysis aims to support research in medical sciences and contribute to understanding diseases.
Base Pairing in A Structure
- In the A structure for deoxyribose nucleic acid, adenine pairs with thymine and guanine pairs with cytosine.
Hydrogen Bonds in DNA
- Hydrogen bonds connect purine position 6 to pyrimidine position 6, facilitating stable base pairing.
Tautomeric Forms Significance
- Considering tautomeric forms is significant for understanding alternative hydrogen bonding patterns that can influence base pairing.
Bases with Novel Features
- Bases with novel features that are of considerable biological interest include adenine and thymine, as well as guanine and cytosine.
Inter-twined Chains in Nucleic Acid Model
- The model proposed by Pauling and Corey consists of three inter-twined chains.
Adenine Pairing Implications
- If adenine forms one member of a pair, it can influence genetic coding and replication fidelity.
Ratio of Nucleotide Bases
- A nearly unity ratio of adenine to thymine and guanine to cytosine indicates reliability in base pairing and contributes to genetic stability.
Van der Waals Distances
- The small van der Waals distances in the proposed DNA structure suggest potential atomic overlap, indicating structural strain or instability.
Ribose vs. Deoxyribose
- It is unlikely to build the proposed structure with ribose sugar instead of deoxyribose due to steric hindrances presented by the additional hydroxyl group.
Significance of Negatively Charged Phosphates
- The negatively charged phosphates near the axis of the proposed structure play a crucial role in the stability of the helix and interaction with cations.
X-ray Diagrams and Salt
- The material providing the X-ray diagrams being the salt, not the free acid, is significant as it affects the diffraction patterns and hence the structural interpretation.
Authors' Overall Assessment
- The authors express cautious optimism about the proposed structure for deoxyribose nucleic acid, recognizing its potential to explain key biological functions while acknowledging areas needing further research.
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Description
Test your knowledge on the pairing rules of DNA bases including purines, pyrimidines, and hydrogen bonding according to the A Structure for Deoxyribose Nucleic Acid model proposed in a Nature article from 1953.
