DNA Structure and Composition Quiz
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Questions and Answers

What is the role of complementary base pairing in DNA?

  • Determines the number of hydrogen bonds in DNA
  • Controls the left-handed twist in the DNA helix
  • Regulates the packaging of DNA into chromosomes
  • Maintains the constant diameter of the DNA helix (correct)

    • Which type of DNA has a left-handed twist in the helix?

  • C-DNA
  • Z-DNA (correct)
  • A-DNA
  • B-DNA

    • What holds base pairs together in DNA?

  • Covalent bonds
  • Hydrogen bonds (correct)
  • Van der Waals forces
  • Ionic bonds

    • In which type of organism is DNA wrapped around proteins called histones?

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

    What is the distance between adjacent bases in the DNA helix?

    <p>~3.4 angstroms</p> Signup and view all the answers

    Which type of DNA is found within cells and is highly hydrated?

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

    What allows DNA to be packaged up in prokaryotes?

    <p>Circular and supercoiled structure</p> Signup and view all the answers

    What contributes to the constant diameter of the DNA helix?

    <p>Complementary base pairing</p> Signup and view all the answers

    What is the structural difference between uracil and thymine?

    <p>Presence of CH3 group on thymine</p> Signup and view all the answers

    Which bases are considered pyrimidines in DNA?

    <p>Thymine and Cytosine</p> Signup and view all the answers

    Which of the following describes nucleosides?

    <p>Bases bonded to the sugar via beta-glycosidic linkage</p> Signup and view all the answers

    What are the building blocks of DNA called?

    <p>Deoxyribonucleoside triphosphates (DNTPs)</p> Signup and view all the answers

    How are nucleotides joined together in DNA?

    <p>Via phosphodiester bonds</p> Signup and view all the answers

    Why does the sequence of bases in DNA go from 5’ to 3’?

    <p>Due to the presence of free OH group on the 5’ carbon of the pentose sugar</p> Signup and view all the answers

    What is the structure of DNA polymer?

    <p>Double helix</p> Signup and view all the answers

    How are the two strands of DNA oriented with respect to each other?

    <p>Anti-parallel</p> Signup and view all the answers

    DNA is a polymer made up of nucleotides.

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

    The sugar-phosphate backbone of DNA remains constant along the length of the polymer.

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

    Thymine and cytosine are pyrimidines.

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

    The structural difference between uracil and thymine is the CH3 group attached to thymine.

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

    Deoxyribonucleoside triphosphates (DNTPs) are the building blocks of RNA.

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

    Nucleotides are joined together via phosphodiester bonds which require ATP.

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

    The strands of DNA are oriented in a parallel manner.

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

    DNA polymer forms a single helix structure.

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

    DNA's sugar-phosphate backbone is located on the inside while the bases are on the outside.

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

    Z-DNA is a highly hydrated form of DNA with a left-handed twist in the helix.

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

    A purine always pairs with another purine in the DNA double helix.

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

    Complementary base pairing in DNA is achieved through the formation of hydrogen bonds.

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

    The ratio of A:T and C:G is similar in nearly all organisms, supporting the theory of complementary base pairing.

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

    Circular DNA molecules can be found in eukaryotic cells and are essential for DNA packaging.

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

    B-DNA, A-DNA, and Z-DNA are all different structural forms of DNA.

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

    Histones are proteins that DNA is wrapped around in prokaryotic organisms.

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

    Study Notes

    Role of Complementary Base Pairing

    • Complementary base pairing in DNA occurs through hydrogen bonds, ensuring accurate pairing: adenine (A) with thymine (T), and cytosine (C) with guanine (G).
    • This pairing stabilizes the double helix structure and maintains the consistent diameter of the DNA molecule.
    • The A:T and C:G ratio remains relatively constant across organisms, reinforcing the concept of complementary base pairing.

    Types of DNA Structure

    • Z-DNA is characterized by a left-handed twist in the helix and is known to be a highly hydrated form of DNA.
    • B-DNA and A-DNA are other structural forms, where B-DNA is the most common form found in cells.

    DNA Components

    • Base pairs in DNA are held together by hydrogen bonds formed through complementary base pairing.
    • DNA is composed of nucleotides, which are the building blocks made up of a sugar, a phosphate group, and a nitrogenous base.
    • A structural difference exists between uracil and thymine, mainly due to the methyl (CH3) group attached to thymine.

    Base Pairing and Orientation

    • In DNA, pyrimidines are represented by thymine (T) and cytosine (C).
    • Nucleosides are composed of a nitrogenous base attached to a sugar, while nucleotides are nucleosides with an additional phosphate group.
    • Nucleotides are joined together by phosphodiester bonds, a process that requires adenosine triphosphate (ATP) as an energy source.

    DNA Structure and Function

    • DNA strands are oriented antiparallel, meaning one runs from the 5’ to 3’ direction while the other runs from 3’ to 5’.
    • The sugar-phosphate backbone remains consistent and forms the inner structure, while the bases face outward.
    • Prokaryotes package their DNA using circular DNA molecules, while eukaryotes wrap DNA around proteins called histones for packaging.

    Summary of DNA Polymers

    • DNA polymer exhibits a single helix structure, with the arrangement of nucleotides determining the genetic information carried within the molecule.
    • The specifics of base pairing and the arrangement of nucleotides play crucial roles in genetic stability and expression.

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    Related Documents

    DNA structure and function.docx

    Description

    Test your knowledge of DNA structure and composition with this quiz. Explore the components of nucleotides, the differences between DNA and RNA, and the key characteristics of purines and pyrimidines.

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