Genetic Implications of DNA Structure
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Questions and Answers

What percentage of H₂O is required to produce A - DNA?

  • 92%
  • 75% (correct)
  • 90%
  • 85%

    • Which DNA type has the average base pairs per turn equal to 10?

  • Z - DNA
  • B - DNA (correct)
  • All types of DNA
  • A - DNA

    • What is the diameter of A - DNA?

  • 1.9 nm
  • 2.5 nm
  • 2.3 nm (correct)
  • 1.8 nm

    • Which direction does B - DNA helix twist?

    <p>Right-handed</p> Signup and view all the answers

    Which DNA type has the distance between adjacent bases of 0.37 nm?

    <p>Z - DNA</p> Signup and view all the answers

    What is the orientation of the two strands in the DNA double helix?

    <p>Both strands are oriented antiparallel.</p> Signup and view all the answers

    Which of the following base pairs are correctly paired in DNA?

    <p>Adenine pairs with Thymine.</p> Signup and view all the answers

    What primarily stabilizes the DNA double helix structure?

    <p>Hydrophobic interactions and van der Waals forces.</p> Signup and view all the answers

    What is the role of high-resolution x-ray diffraction studies in understanding DNA?

    <p>They provide structural models of DNA.</p> Signup and view all the answers

    What major contribution did Watson and Crick make to the field of genetics?

    <p>They elucidated the chemical structure of DNA.</p> Signup and view all the answers

    Which of the following is a fundamental property of genetic material identified by Watson and Crick?

    <p>Capacity to carry large amounts of information.</p> Signup and view all the answers

    What type of bonds hold the complementary base pairs together in DNA?

    <p>Hydrogen bonds.</p> Signup and view all the answers

    How does the sequence of the four bases in DNA relate to phenotypes?

    <p>It encodes information determining the phenotype.</p> Signup and view all the answers

    Which statement about synthetic DNAs is true?

    <p>They can form other, non-standard base pairs.</p> Signup and view all the answers

    What mechanism did Watson and Crick propose for DNA replication?

    <p>DNA strands unzip and serve as templates.</p> Signup and view all the answers

    What is meant by 'base pair complementarity' in DNA?

    <p>The consistent pairing between specific bases.</p> Signup and view all the answers

    What contributes to the precise alignment of the two DNA strands?

    <p>Hydrogen bonds between paired bases.</p> Signup and view all the answers

    What suggestion did Watson and Crick highlight regarding base pairing during replication?

    <p>It specifies only one possible complementary sequence.</p> Signup and view all the answers

    Which of the following bases is NOT part of the DNA structure according to Watson and Crick?

    <p>Uracil</p> Signup and view all the answers

    What was the significance of the double helix structure proposed by Watson and Crick?

    <p>It suggested a mechanism for DNA replication.</p> Signup and view all the answers

    Why was the establishing of DNA's structure pivotal in the study of molecular genetics?

    <p>It made direct examination of genes possible.</p> Signup and view all the answers

    What critical feature of DNA makes it more stable than RNA?

    <p>The absence of a 2’-hydroxyl group</p> Signup and view all the answers

    How do the 2’-hydroxyl groups in RNA influence its stability?

    <p>They are involved in the hydrolysis of phosphodiester bonds.</p> Signup and view all the answers

    Which structure is proposed for deoxyribose nucleic acid (DNA)?

    <p>Three intertwined chains with phosphates near the fiber axis</p> Signup and view all the answers

    Why is the structure proposed by Pauling and Corey considered unsatisfactory?

    <p>The negatively charged phosphates would repel each other.</p> Signup and view all the answers

    What role do the bases play in the proposed structure of DNA?

    <p>They are located on the outside of the structure.</p> Signup and view all the answers

    What happens to the RNA when the 2’-hydroxyl group acts as a nucleophile?

    <p>It hydrolyzes the phosphodiester bond.</p> Signup and view all the answers

    Which of the following statements about the deoxyribose sugar is correct?

    <p>It lacks a hydroxyl group at the 2’ position.</p> Signup and view all the answers

    What is a significant consequence of RNA's structure compared to DNA's?

    <p>RNA can undergo hydrolysis more easily than DNA.</p> Signup and view all the answers

    What is the primary structural difference between A-form and B-form DNA?

    <p>A-form has deeper major and shallower minor grooves.</p> Signup and view all the answers

    How far apart are adjacent stacked base pairs in B-form DNA?

    <p>0.34 nm apart</p> Signup and view all the answers

    What characteristic of DNA allows it to bend when complexed with a DNA-binding protein?

    <p>Flexibility along its long axis</p> Signup and view all the answers

    Which part of DNA allows for distinguishing between different bases?

    <p>The major and minor grooves</p> Signup and view all the answers

    What is the role of the TATA box-binding protein (TBP) in relation to DNA?

    <p>It binds to the minor groove, bending the double helix.</p> Signup and view all the answers

    What modification occurs to B-form DNA in response to protein binding?

    <p>Altered stability from hydrogen and hydrophobic bonds</p> Signup and view all the answers

    What is the approximate number of base pairs in one helical turn of B-form DNA?

    <p>10.5 base pairs</p> Signup and view all the answers

    How do hydrogen and hydrophobic bonds contribute to DNA?

    <p>They provide stability to the DNA structure.</p> Signup and view all the answers

    What type of configuration is close to Furberg's standard in the described structure?

    <p>The sugar is perpendicular to the bases.</p> Signup and view all the answers

    What are the bases paired together through in this structure?

    <p>Hydrogen bonds.</p> Signup and view all the answers

    How often does the structure repeat in terms of residues in each chain?

    <p>Every 10 residues.</p> Signup and view all the answers

    Which pairs of bases can bond together according to the given information?

    <p>Adenine with Thymine.</p> Signup and view all the answers

    What is the distance of a phosphorus atom from the fibre axis in the described structure?

    <p>10 A.</p> Signup and view all the answers

    What factor contributes to the open structure of the molecule?

    <p>High water content.</p> Signup and view all the answers

    Which configuration between the bases occurs for pairing to be successful?

    <p>One must be a purine, the other must be a pyrimidine.</p> Signup and view all the answers

    At what angle do adjacent residues in the same chain of the structure orient?

    <p>36 degrees.</p> Signup and view all the answers

    Study Notes

    Genetic Implications of DNA Structure

    • DNA is the physical structure that holds the genotype
    • Watson and Crick elucidated DNA's chemical structure, allowing for direct gene examination
    • DNA structure revealed the birth of molecular genetics, focusing on the chemical and molecular nature of genetic information
    • DNA structure provides insight into fundamental genetic processes
    • DNA must carry large amounts of information, varying in structure
    • Genetic instructions are encoded in base sequence (adenine, guanine, cytosine, and thymine)
    • The order of bases dictates the phenotype
    • Watson and Crick recognized the necessity of faithful DNA replication
    • Complementary polynucleotide strands facilitate replication
    • The specific base pairing suggests a copying mechanism where strands unzip, and new strands are synthesized based on existing templates

    Structural model for double helix DNA

    • James Watson and Francis Crick proposed the double helix structure in 1953, explaining how DNA carries genetic information
    • Maurice Wilkins and Rosalind Franklin's X-ray diffraction images provided crucial data for Crick and Watson's model
    • The double helix is composed of two polynucleotide strands, with sugar-phosphate backbones on the outside and bases inside
    • DNA strands are antiparallel (5' to 3' directions are opposite)
    • Bases pair specifically (A with T; G with C) via hydrogen bonds, stabilizing the structure

    Native DNA is a Double Helix of Complementary Antiparallel Strands

    • DNA exists as a double helix composed of two antiparallel strands
    • James Watson and Francis Crick proposed this structure in 1953
    • Rosalind Franklin's and Maurice Wilkins' X-ray diffraction data supported the model
    • Base composition (A=T and G=C) of DNA remains consistent in different species
    • Hydrogen-bonded base pairs (A-T and G-C) are essential for DNA structure

    DNA Structure Details

    • DNA consists of two polynucleotide chains that are twisted to form a double helix
    • The two strands are antiparallel.
    • The sugar-phosphate backbones form the outside of the double helix
    • Bases are stacked inside the double helix.
    • Bases form base pairs to stabilize structure.. (adenine with thymine; guanine with cytosine).

    A-Form, B-Form, and Z-Form DNA

    • DNA exists in various forms (A, B, Z) with slight structural variations influenced by factors like water content and protein binding.

    Access to Information within the Double Helix

    • The grooves in the DNA double helix allow for access to bases without breaking the DNA structure
    • RNA is less stable than DNA due to a hydroxyl group at the 2' carbon of the ribose sugar, making RNA susceptible to hydrolysis, versus the more stable deoxyribose of DNA.

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    Lecture (2): Genetic Implications of DNA Structure PDF

    Description

    Explore the groundbreaking discoveries of Watson and Crick regarding the structure of DNA and its significance in genetics. This quiz delves into how DNA encodes genetic information, the process of replication, and the molecular basis behind phenotypes. Test your knowledge on the fundamental principles of molecular genetics.

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