Biochemistry Chapter 8 Quiz
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Questions and Answers

Classify the description as pertaining to nucleosides, nucleotides, or both nucleosides and nucleotides.

  • Nucleosides (correct)
  • Both (correct)
  • Nucleotides (correct)

    • What is the DNA sequence complementary to AGTC?

    TCAG

    Classify the statements as describing deoxyribonucleic acid (DNA) or ribonucleic acid (RNA).

  • DNA (correct)
  • RNA (correct)

    • What intermolecular force is responsible for holding the two strands of a DNA double helix together?

    <p>Hydrogen bond</p> Signup and view all the answers

    What is a phosphodiester bond?

    <p>A covalent bond that forms the backbone of DNA and RNA molecules</p> Signup and view all the answers

    Which DNA molecule has a lower percentage of G-C base pairs that stabilize DNA duplexes?

    <p>DNA 1</p> Signup and view all the answers

    How does the structure of DNA encode genetic information?

    <p>The sequence of bases</p> Signup and view all the answers

    What are the stabilizing factors that hold the two strands of DNA together in a double helix?

    <p>Hydrogen bonding, Base stacking, Hydrophobic interactions</p> Signup and view all the answers

    In Watson-Crick base pairing in DNA, guanine pairs with?

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

    The phosphate groups are on the outside of the DNA double helix because they are charged and interact with the aqueous environment surrounding the DNA.

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

    What contribution did James Watson and Francis Crick make to our understanding of DNA?

    <p>They modeled the structure of DNA based on the limited data available</p> Signup and view all the answers

    Choose the statement that explains why organisms use DNA as the central repository for genetic information.

    <p>DNA is more resistant against enzymes that break down nucleic acids.</p> Signup and view all the answers

    Match the structure names to the descriptions given.

    <p>Hairpin Structure = A structure that may be formed from a single DNA strand with the sequence -ATATG.....CATAT- G tetraplex = Four-stranded, right-handed helix formed by a DNA segment containing a high proportion of guanine residues Cruciform structure = A structure formed when interstrand hydrogen bonds break and intrastrand hydrogen bonds form Triplex DNA = A polynucleotide strand that forms Hoogsteen pairs with functional groups in the major groove of a homopurine-homopyrimidine duplex</p> Signup and view all the answers

    What is small nuclear RNA?

    <p>snRNA; involved in the splicing process when mRNA is formed</p> Signup and view all the answers

    What is ribosomal RNA?

    <p>rRNA; Combines with proteins to form ribosomes</p> Signup and view all the answers

    What is transfer RNA?

    <p>tRNA; Brings amino acids to sites of mRNA during protein synthesis</p> Signup and view all the answers

    What is small interfering RNA?

    <p>siRNA; Eliminates the expression of an undesirable gene</p> Signup and view all the answers

    What is messenger RNA?

    <p>mRNA; Carries genetic information to ribosomes for protein synthesis</p> Signup and view all the answers

    What is micro RNA?

    <p>miRNA; Inhibits the translation of mRNA into protein</p> Signup and view all the answers

    In bacteria, which two bases undergo methylation more often?

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

    What are the functions of nucleic acids?

    <p>Nucleic acids are polymers of nucleotides used for: Storage of genetic information (DNA), Transmission of genetic information (mRNA), Processing of genetic information (ribozymes), Protein synthesis (tRNA and rRNA)</p> Signup and view all the answers

    What are the functions of nucleotides?

    <p>Nucleotides are also used in the monomer form for cellular functions: Energy for metabolism (ATP), Enzyme cofactors (NAD+), Signal transduction (cAMP)</p> Signup and view all the answers

    What are the components of a nucleotide?

    <p>Nitrogenous base, Pentose, Phosphate</p> Signup and view all the answers

    What are the components of a nucleoside?

    <p>Nitrogenous base, Pentose</p> Signup and view all the answers

    What is a phosphate group?

    <p>A molecule in the backbone of DNA and RNA that links adjoining bases together; Negatively charged at neutral pH; Typically attached to 5' position</p> Signup and view all the answers

    What is a nitrogenous base?

    <p>Derivatives of pyrimidine or purine; Nitrogen-containing heteroaromatic molecules; Absorb UV light around 250-270 nm</p> Signup and view all the answers

    What are minor nucleosides in DNA?

    <p>Modification is done after DNA synthesis; Common examples include 5-methylcytosine and N6-methyladenosine</p> Signup and view all the answers

    What is inosine?

    <p>Inosine is sometimes found in the 'wobble position' of the anticodon in tRNA; Provides richer genetic code</p> Signup and view all the answers

    What is pseudouridine?

    <p>Pseudouridine is found widely in tRNA and rRNA; May stabilize the structure of tRNA</p> Signup and view all the answers

    What are prototropic tautomers?

    <p>Structural isomers that differ in the location of protons</p> Signup and view all the answers

    Where is keto-enol tautomerism common?

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

    Where does lactam-lactim tautomerism occur?

    <p>In some heterocycles; Forms a predominance at neutral pH</p> Signup and view all the answers

    What are polynucleotides?

    <p>Polymers of nucleic acids</p> Signup and view all the answers

    How are covalent bonds formed?

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

    Is the DNA backbone stable?

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

    Is the RNA backbone unstable?

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

    What is meant by linear polymers?

    <p>No branching or cross-links</p> Signup and view all the answers

    What is hydrolysis of RNA?

    <p>RNA is unstable under alkaline conditions; RNase enzymes are abundant around us</p> Signup and view all the answers

    What are hydrogen bonding interactions?

    <p>Two bases can hydrogen bond to form a base pair; Watson and Crick base pairs predominate in double-stranded DNA</p> Signup and view all the answers

    What is replication of genetic code?

    <p>Strand separation occurs first; Each strand serves as a template for the synthesis of a new strand</p> Signup and view all the answers

    What is a beta-N-glycosidic bond?

    <p>In nucleotides, the pentose ring is attached to the nitrogenous base via an N-glycosidic bond</p> Signup and view all the answers

    What is conformation around N-Glycosidic Bond?

    <p>Relatively free rotation can occur; The bond is found in both syn and anti configurations</p> Signup and view all the answers

    What is DNA denaturation?

    <p>Covalent bonds and genetic code remain intact; Hydrogen bonds are broken; Base stacking is lost</p> Signup and view all the answers

    What are factors affecting DNA denaturation?

    <p>The midpoint of melting (Tm) depends on base composition; High CG increases Tm</p> Signup and view all the answers

    What are applications of near-complementary hybrid in DNA and RNA?

    <p>Detection of a specific DNA molecule in complex mixtures; Amplification of specific DNA;</p> Signup and view all the answers

    What is deamination?

    <p>Very slow reactions; Net effect is significant: 100 C --&gt; U events/day in a mammalian cell</p> Signup and view all the answers

    What is depurination?

    <p>N-glycosidic bond is hydrolyzed; Significant for purines: 10,000 purines lost/day in a mammalian cell</p> Signup and view all the answers

    What is oxidative damage?

    <p>Hydroxylation of guanine; Mitochondrial DNA is most susceptible</p> Signup and view all the answers

    What is chemical alkylation?

    <p>Methylation of guanine</p> Signup and view all the answers

    What are molecular mechanisms of radiation-induced mutagenesis?

    <p>UV light induces dimerization of pyrimidines; Ionizing radiation causes ring opening and strand breaking</p> Signup and view all the answers

    Study Notes

    Nucleic Acids: Structure and Function

    • Nucleosides consist of a base and a pentose sugar, while nucleotides contain a phosphate group in addition to the base and sugar.
    • DNA sequences can be complementary, with A pairing with T and C pairing with G.
    • DNA is typically double-stranded and stable, while RNA is mostly single-stranded and more susceptible to hydrolysis.

    Intermolecular Forces and Bonding

    • Hydrogen bonds stabilize the DNA double helix structure.
    • Phosphodiester bonds form the sugar-phosphate backbone, linking nucleotides covalently.
    • Base stacking and hydrophobic interactions further stabilize DNA double helices.

    DNA Structural Variations

    • Sequence-dependent variations, such as hairpin, G-quadruplex, cruciform, and triplex structures, can influence DNA's function.
    • Methylation of adenine and cytosine bases commonly occurs in bacteria, serving as an epigenetic marker.

    Nucleic Acid Types and Functions

    • Nucleic acids have various functional roles: DNA stores genetic information, mRNA transmits information, tRNA and rRNA are involved in protein synthesis.
    • Minor nucleosides like inosine and pseudouridine play crucial roles in genetic code diversity and RNA stability.

    Tautomerism and Stability

    • Prototropic tautomers are structural isomers with differing proton locations; common in nucleotide bases.
    • Keto-enol and lactam-lactim tautomerism can affect nucleotide stability and interactions.

    Generating and Modifying Nucleic Acids

    • Covalent bonds through phosphodiester linkages form polynucleotide chains, critical for genetic information replication.
    • DNA denaturation involves breaking hydrogen bonds, leading to increased UV absorbance, which can be reversible under certain conditions.

    Mutagenesis and Genetic Integrity

    • Deamination and depurination represent common forms of DNA damage, with significant consequences for genetic stability.
    • Chemical alkylation and oxidative damage can modify DNA bases, influencing mutation rates linked to aging and diseases such as cancer.

    Applications and Techniques

    • Near-complementary hybrids in DNA and RNA are used in detecting specific sequences and amplifying DNA via techniques like PCR.
    • Antisense therapy and fluorescent DNA chips utilize hybridization methods for therapeutic and research applications.

    Key Terminology

    • Nucleoside: Base + Pentose Sugar.
    • Nucleotide: Nucleoside + Phosphate.
    • TM (Melting Temperature): Higher with more G-C pairs or longer DNA sequences.
    • Hydrogen Bonding: Pairs bases in DNA; crucial for duplex stability.
    • RNA Hydrolysis: Mostly unstable due to its structure, leading to rapid degradation.

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    Description

    Test your knowledge on nucleosides and nucleotides with this chapter 8 quiz. Classify the definitions provided and see how well you understand these essential components of nucleic acids. Perfect for students focusing on biochemistry topics.

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