Nucleic Acids: Structure and Function Quiz
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Questions and Answers

What is the primary function of DNA topoisomerases during DNA replication?

  • Seal nicks in the DNA
  • Relieve torsional stress (correct)
  • Initiate RNA synthesis
  • Unwind the double helix

    • Which of the following accurately describes the role of helicase in DNA replication?

  • Seals nicks left by DNA polymerase
  • Initiates synthesis of RNA primers
  • Removes supercoils formed during replication
  • Unwinds the double helix (correct)

    • What distinguishes eukaryotic DNA polymerases from prokaryotic ones?

  • Involvement in telomere maintenance
  • Distinct activities and types (correct)
  • Presence of RNA primers
  • Ability to proofread

    • What is the primary function of telomeres at the ends of eukaryotic chromosomes?

    <p>Prevent attack by nucleases</p> Signup and view all the answers

    Which of the following statements about telomerase is correct?

    <p>It maintains telomere length</p> Signup and view all the answers

    What are the components of a nucleotide?

    <p>A sugar, a base, and a phosphate group</p> Signup and view all the answers

    What type of bond is formed between nucleotides in nucleic acids?

    <p>Covalent bonds</p> Signup and view all the answers

    How many base pairs approximately are in one complete turn of the DNA double helix?

    <p>10 base pairs</p> Signup and view all the answers

    What is the term for the complete genetic code of an organism?

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

    What type of RNA is produced from the genetic code of a gene?

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

    Which of the following accurately describes the strands of DNA?

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

    What distinguishes DNA from RNA in terms of their sugar component?

    <p>RNA has a ribose sugar</p> Signup and view all the answers

    Which proteins are the major components of chromatin?

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

    What is the effect of histone acetylation on chromatin structure?

    <p>Decreases DNA affinity and decompacts chromatin</p> Signup and view all the answers

    How does DNA replication in eukaryotes differ from prokaryotes?

    <p>Eukaryotic DNA replication is bidirectional with multiple origins</p> Signup and view all the answers

    What role does helicase play during DNA replication?

    <p>Maintains separation of parental DNA strands</p> Signup and view all the answers

    What accurately describes the leading and lagging strands during replication?

    <p>Leading strand is synthesized continuously while lagging strand is discontinuous</p> Signup and view all the answers

    What distinguishes the end of a chromosome from a double strand break?

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

    What is the initial requirement for DNA polymerases during DNA synthesis?

    <p>A template DNA strand and a primer with a free 3' end</p> Signup and view all the answers

    What was a significant finding regarding Dolly the sheep's telomeres?

    <p>They were shorter than expected for her chronological age.</p> Signup and view all the answers

    Why is DNA replication described as semi-conservative?

    <p>Each daughter molecule contains one parental and one new strand</p> Signup and view all the answers

    What happens to telomeres in normal human somatic cells with successive cell divisions?

    <p>They shorten.</p> Signup and view all the answers

    What is the primary function of nucleosomes in eukaryotic DNA?

    <p>To package and condense DNA</p> Signup and view all the answers

    Which of the following conditions allows cancer and stem cells to continue dividing without telomere shortening?

    <p>Enhancement of telomerase activity.</p> Signup and view all the answers

    What is the significance of RNA primers during DNA replication?

    <p>They serve as the starting point for DNA polymerase</p> Signup and view all the answers

    Which anticancer drug replaces deoxyribose with arabinose to inhibit DNA synthesis?

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

    What is a common environmental agent that causes damage to DNA?

    <p>UV radiation</p> Signup and view all the answers

    What is defined as a heritable change in the sequence of nucleotides in DNA?

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

    What is the primary purpose of telomeres in cells?

    <p>To protect chromosome ends.</p> Signup and view all the answers

    What are the two types of nucleic acids?

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

    Which of the following bases is not found in DNA?

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

    What is the primary function of DNA in a cell?

    <p>To store genetic information</p> Signup and view all the answers

    What distinguishes deoxyribose from ribose?

    <p>Deoxyribose has an H instead of an OH group at the 2’ position</p> Signup and view all the answers

    Which molecule serves as the major players in the cell, influencing rates of reactions?

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

    What is the term for the unidirectional flow of genetic information?

    <p>Central dogma of molecular biology</p> Signup and view all the answers

    How many different bases are found in nucleic acids?

    <p>5 in RNA and 4 in DNA</p> Signup and view all the answers

    What type of genetic information does the nuclear genome primarily contain?

    <p>Maternal and paternal genetic information</p> Signup and view all the answers

    Study Notes

    Nucleic Acids: Structure and Function

    • Nucleic acids are composed of nucleotide building blocks (polynucleotides)
    • Two types: ribonucleic acid (RNA) and deoxyribonucleic acid (DNA)
    • Each nucleotide consists of a base, a sugar, and one or more phosphate groups
    • Bases are nitrogen-containing molecules
    • Five different bases: adenine (A), cytosine (C), guanine (G), thymine (T), and uracil (U)
    • A, C, G, and U are found in RNA
    • A, C, G, and T are found in DNA
    • Purines: A and G
    • Pyrimidines: C, T, and U
    • Sugars are monosaccharides (pentoses)
    • Ribose is in RNA
    • Deoxyribose is in DNA
    • Deoxyribose has a H instead of an OH group at the 2' position
    • Phosphates can be mono-, di-, or tri-phosphate groups
    • Examples include adenosine monophosphate (AMP), adenosine diphosphate (ADP), and adenosine triphosphate (ATP)
    • Nucleotides are joined through 3'-5' phosphodiester linkages (covalent bonds)
    • Nucleic acids are directional, having 5' and 3' ends
    • Sequence of bases is not restricted, storing genetic information
    • Bases interact via hydrogen bonds in base pairing
    • A pairs with T (in DNA) or U (in RNA)
    • G pairs with C
    • Hydrogen bonds are individually weak
    • Base pairing is specific
    • DNA is a double helix
    • Two strands coil around the same axis
    • Approximately 10 base pairs per turn
    • Length of DNA expressed in base pairs (bp)
    • 1000 base pairs = 1 kilobase pair (1 kb)
    • Human genome has about 3.2 x 109 base pairs
    • DNA strands run in opposite directions; antiparallel
    • Chemical structure of double-stranded DNA (dsDNA)

    DNA Replication

    • DNA replication is semi-conservative
    • Each strand of DNA serves as a template for a new strand
    • Each daughter molecule contains one parental strand and one newly synthesized strand
    • DNA replication is bidirectional with multiple origins of replication
    • Replication is primed by short stretches of RNA
    • Replication is semidiscontinuous
    • DNA polymerase is needed for synthesis. It requires a template strand, dNTPs, and a primer with a free 3' end.
    • The leading strand is synthesized continuously, while the lagging strand is synthesized discontinuously in short fragments called Okazaki fragments
    • RNA primers are needed for lagging strand synthesis
    • Primase is DNA-directed RNA polymerase
    • DNA polymerase I removes RNA primers and fills the gaps
    • DNA ligase seals the nicks
    • DNA helicase unwinds the double helix ahead of the replication fork
    • Single-stranded DNA-binding proteins keep the two strands separate during replication
    • Topoisomerases relieve torsional stress in DNA during replication
    • Eukaryotic DNA polymerases have different functions (alpha, beta, delta, epsilon, gamma). Pol alpha inits. DNA synthesis. Pol beta is related to repair. Pol de/ep for lagging/leading strand elongation. Pol is involved in mitochondrial replication

    Eukaryotic Cell Cycle

    • The cell cycle includes G1, S, G2, and M phases
    • S phase includes DNA replication
    • G phases are gap phases for cell growth
    • M phase includes mitosis (chromosomes segregate)
    • Cells that have ceased division are in G0 phase

    Eukaryotic DNA Polymerases

    • Eukaryotic cells contain various DNA polymerases with specific functions
    • Pol α (alpha) initiates DNA synthesis
    • Pol β (beta) is related to repair
    • Pol δ/ε (delta, epsilon) synthesize the lagging/leading strands

    Telomeres

    • Telomeres are repetitive DNA stretches at chromosome ends, complexed with proteins
    • The telomere sequence in humans is (TTAGGG)n
    • Telomeres shorten with each cell division
    • Shortened telomeres prevent cell division
    • Cancer and stem cell telomeres do not shorten
    • Telomerase is a telomere maintenance enzyme that maintains telomere length

    DNA Damage

    • Environmental agents (chemicals, radiation) can damage DNA
    • Errors in normal cellular processes can cause DNA damage
    • Normal chemical changes (e.g., oxidation) can damage DNA
    • Mutations are heritable changes in the DNA sequence

    Medical Relevance

    • Telomeres shorten in normal somatic cells with each division
    • Once the telomeres get too short, cells can't divide anymore
    • Cancer and stem cells have high telomerase activity which allow continuous division
    • DNA synthesis can be inhibited by nucleoside analogs, such as AZT (zodovudine) – a modified sugar component
    • AZT is an anti-retroviral drug
    • Cytosine arabinoside is anti-cancer drug

    Causes of DNA Damage

    • Environmental agents like chemicals and radiation (e.g., UV radiation causes adjacent T's to dimerize)
    • Errors during normal cellular processes (e.g., incorrect nucleotide incorporation during DNA replication)
    • Normal chemical alterations (e.g., oxidation)

    Supercoils and Topoisomerases

    • As DNA unwinds during replication, supercoils form
    • DNA topoisomerases remove supercoils to prevent torsional stress
    • Certain antimicrobial and cancer drugs target topoisomerases as a mechanism of action

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    Related Documents

    DNA Structure and Replication PDF

    Description

    Test your knowledge on the structure and function of nucleic acids, including DNA and RNA. This quiz covers nucleotide composition, types of bases, and the significance of sugars and phosphates in nucleic acids. Explore the essential concepts of molecular biology that define genetic information.

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