DNA Structure & Replication Quiz
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Questions and Answers

If a strand of DNA has the sequence 5'-GCTTAG-3', what would be the sequence of its complementary strand?

  • 3'-GCTTAG-5'
  • 5'-CTAAGC-3'
  • 3'-CGAATC-5' (correct)
  • 5'-CGAAUC-3'

    • During a cell division, DNA replication must occur. What is the PRIMARY reason DNA replicates semi-conservatively?

  • To maximize the number of replication forks
  • To minimize the risk of mutations during the process.
  • To ensure the newly created DNA strands are identical to the original ones.
  • To maintain the complementary base pairing structure of DNA. (correct)

    • What is the direct relationship between genes and proteins?

  • Genes determine the sequence of amino acids which make up the protein. (correct)
  • Genes determine the post-translational modification of proteins.
  • Genes regulate the synthesis of protein-building enzymes.
  • Genes directly code for proteins' secondary structure.

    • In transcription, RNA is synthesized using a DNA template. What is one key difference in base pairing between transcription and DNA replication?

    <p>A pairs up with U in transcription instead of T. (B)</p> Signup and view all the answers

    What is the main relationship between an organism's genes, the proteins they produce, and the organism's physical traits?

    <p>Genes code for proteins, which in turn influence the organism's structure and function. (B)</p> Signup and view all the answers

    What mechanism suggested by Watson and Crick is essential for DNA replication?

    <p>Specific base pairing (A)</p> Signup and view all the answers

    Which statements accurately describe the process of DNA replication?

    <p>Replication begins at multiple origins on the DNA molecule. (C)</p> Signup and view all the answers

    What role do enzymes and proteins play in DNA replication?

    <p>They work together to ensure speed and accuracy. (D)</p> Signup and view all the answers

    How do the daughter strands in DNA replication form?

    <p>They are synthesized using the complementary sequences of the template strands. (B)</p> Signup and view all the answers

    What occurs at the origins of replication in a DNA molecule?

    <p>The two strands of DNA are separated, creating a replication bubble. (C)</p> Signup and view all the answers

    Which of the following accurately describes the flow of genetic information within a eukaryotic cell?

    <p>DNA → mRNA → protein (C)</p> Signup and view all the answers

    What is the role of mRNA in protein synthesis?

    <p>It carries the genetic code from the DNA to the ribosomes. (A)</p> Signup and view all the answers

    Which of the following best describes the relationship between a gene and a polypeptide?

    <p>A gene is a segment of DNA that contains the instructions for the amino acid sequence of a polypeptide. (D)</p> Signup and view all the answers

    What type of bond connects adjacent nucleotides in a polynucleotide chain?

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

    In a DNA double helix, which nitrogenous bases pair with each other?

    <p>Adenine with thymine, and guanine with cytosine (C)</p> Signup and view all the answers

    What is the significance of the antiparallel arrangement of DNA strands?

    <p>It enables the correct base pairing between the two strands. (B)</p> Signup and view all the answers

    Which component is NOT a part of a nucleoside?

    <p>Phosphate group (A)</p> Signup and view all the answers

    In what location within a eukaryotic cell does transcription primarily occur?

    <p>Nucleus (B)</p> Signup and view all the answers

    What distinguishes pyrimidines from purines in terms of their structure?

    <p>Purines have a single six-membered ring, while pyrimidines have a six-membered ring fused to a five-membered ring. (A)</p> Signup and view all the answers

    Which of the following is NOT a component of a DNA nucleotide?

    <p>Uracil (A)</p> Signup and view all the answers

    A segment of DNA has the sequence 5'-ATCGG-3'. What would be the sequence of its complementary strand?

    <p>3'-TAGCC-5' (B)</p> Signup and view all the answers

    What is the specific role of ribosomes in the protein synthesis process?

    <p>They translate mRNA into the amino acid sequence of a polypeptide. (D)</p> Signup and view all the answers

    Which of the following best describes the overall function of DNA?

    <p>It directs development of various traits. (C)</p> Signup and view all the answers

    What are the two main types of nucleic acids?

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

    Why are the two strands of the DNA double helix considered complementary?

    <p>The nitrogenous bases pair specifically (A with T, and G with C). (A)</p> Signup and view all the answers

    Which of the following steps in DNA replication relies on the activity of primase?

    <p>The formation of Okazaki fragments on the lagging strand. (B)</p> Signup and view all the answers

    What is the primary function of topoisomerase in DNA replication?

    <p>To prevent the DNA from becoming overwound ahead of the replication fork. (B)</p> Signup and view all the answers

    During DNA replication, which enzyme is responsible for synthesizing the new DNA strand in the 5' to 3' direction?

    <p>DNA polymerase (B)</p> Signup and view all the answers

    Why is it necessary for DNA polymerase to proofread its work during DNA replication?

    <p>To prevent mutations from arising in the newly synthesized DNA. (B)</p> Signup and view all the answers

    How does the structure of a nucleotide differ from that of a nucleoside?

    <p>A nucleotide has a phosphate group attached to the sugar, while a nucleoside does not. (B)</p> Signup and view all the answers

    If a DNA sequence reads 5'-ATGC-3', what would the sequence of the complementary strand be?

    <p>3'-TACG-5' (A)</p> Signup and view all the answers

    How does the antiparallel structure of the DNA double helix affect DNA replication?

    <p>It determines the direction of DNA synthesis on the lagging strand. (C)</p> Signup and view all the answers

    Which of the following is NOT a function of the DNA replication complex?

    <p>Correcting errors in DNA replication. (A)</p> Signup and view all the answers

    Which of the following statements is TRUE about Okazaki fragments?

    <p>They are short fragments of DNA synthesized on the lagging strand. (B)</p> Signup and view all the answers

    What is the role of the sliding clamp in DNA replication?

    <p>To hold DNA polymerase onto the DNA template strand. (A)</p> Signup and view all the answers

    Which of the following is NOT a type of DNA repair mechanism?

    <p>Transcription repair (B)</p> Signup and view all the answers

    Why is it important that DNA replication is semi-conservative?

    <p>It ensures that each new DNA molecule has one parental strand and one new strand. (A)</p> Signup and view all the answers

    Which of the following statements is TRUE about the relationship between DNA polymerase and primase?

    <p>Primase lays down RNA primers, and DNA polymerase extends those primers by adding DNA nucleotides. (D)</p> Signup and view all the answers

    How does the process of DNA replication differ between prokaryotes and eukaryotes?

    <p>Prokaryotes have a single origin of replication, while eukaryotes have multiple. (A)</p> Signup and view all the answers

    How does the presence of telomeres at the ends of linear chromosomes contribute to DNA replication in eukaryotes?

    <p>They prevent the shortening of the chromosomes during replication. (D)</p> Signup and view all the answers

    Which of the following statements is TRUE about the relationship between DNA replication and cell division?

    <p>DNA replication must occur before cell division can begin. (A)</p> Signup and view all the answers

    Study Notes

    DNA Structure & Replication

    • James Watson and Francis Crick introduced the double-helical model of DNA in 1953
    • DNA is the hereditary material, the most important molecule for inheritance
    • Hereditary information is encoded in DNA and replicated in all body cells
    • This DNA program directs the development of biochemical, anatomical, physiological, and behavioral traits

    Nucleic Acid Structure

    • There are two types of nucleic acids: Deoxyribonucleic acid (DNA) and Ribonucleic acid (RNA)
    • DNA provides instructions for its own replication. As a cell divides, its genetic instructions are passed to each daughter cell
    • DNA directs the synthesis of messenger RNA (mRNA) and, through mRNA, controls protein synthesis
    • Protein synthesis occurs in ribosomes
    • Nucleic acids are polymers called polynucleotides
    • Each polynucleotide is made of monomers called nucleotides
    • Each nucleotide consists of a nitrogenous base, a pentose sugar, and a phosphate group
    • The portion of a nucleotide without the phosphate group is called a nucleoside

    Nucleotide Monomers

    • Two families of nitrogenous bases:
      • Pyrimidines (cytosine, thymine, and uracil) have a single six-membered ring
      • Purines (adenine and guanine) have a six-membered ring fused to a five-membered ring
    • In DNA, the sugar is deoxyribose; in RNA, the sugar is ribose

    DNA Double Helix

    • A DNA molecule has two polynucleotides spiraling around an imaginary axis, forming a double helix
    • The two backbones run in opposite 5' to 3' directions, forming an antiparallel arrangement
    • DNA molecules include many genes
    • Nitrogenous bases pair up and form hydrogen bonds: adenine (A) always with thymine (T), and guanine (G) always with cytosine (C)

    DNA Replication

    • DNA replication is remarkable for its speed and accuracy. Many proteins and enzymes are involved
    • Replication begins at specific sites called origins of replication, creating a replication "bubble"
    • Replication proceeds in both directions from each origin, until the entire molecule is copied
    • Helicases untwist the double helix at replication forks.
    • Single-strand binding proteins bind to and stabilize single-stranded DNA
    • Topoisomerase corrects overwinding ahead of replication forks by breaking, swiveling, and rejoining DNA strands
    • DNA polymerases cannot initiate synthesis; they can only add nucleotides to the 3' end
    • The initial nucleotide strand is a short RNA primer
    • An enzyme called primase can synthesize an RNA chain from scratch using a DNA template as a guide. The primer is short (~5-10 nucleotides long), with a free 3' end
    • Each nucleotide is a nucleoside triphosphate (e.g., dATP). As each monomer joins the DNA strand it loses two phosphate groups to provide energy
    • Elongation occurs in the 5' to 3' direction on the leading strand
    • The lagging strand is synthesized as a series of segments called Okazaki fragments, which are joined together by DNA ligase
    • Many proteins work together in a "DNA replication machine," which may be stationary during replication
    • DNA polymerases proofread newly made DNA; replacing any incorrect nucleotides
    • Enzymes correct errors in base pairing (mismatch repair)
    • DNA can be damaged by harmful chemicals or physical agents. Damage repair mechanisms (e.g., nucleotide excision repair) exist
    • Errors occur and can cause changes in the following generation. This provides the raw material for evolution

    Replicating Ends of DNA Molecules

    • Limitations of DNA polymerase create problems for the linear DNA of eukaryotic chromosomes.
    • Telomeres, special nucleotide sequences at the ends of eukaryotic chromosomes, postpone the erosion of genes at the ends of DNA molecules.
    • The enzyme telomerase catalyzes the lengthening of telomeres in germ cells. The shortening of telomeres may protect cells from cancerous growth by limiting the number of cell divisions.

    Chromosome Structure

    • The bacterial chromosome is a double-stranded, circular DNA molecule associated with a small amount of protein.
    • Eukaryotic chromosomes have linear DNA molecules associated with a large amount of protein
    • In a bacterium, the DNA is "supercoiled" and found in a region of the cell called the nucleoid
    • Chromatin, a complex of DNA and protein, is found in the nucleus of eukaryotic cells.
    • Chromosomes fit into the nucleus via a multilevel system of packing, using proteins like histones.

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    DNA Structure & Replication PDF

    Description

    Test your knowledge on the double-helical model of DNA introduced by Watson and Crick in 1953. Explore the roles of DNA and RNA in genetic inheritance and protein synthesis. This quiz covers key concepts related to nucleic acids and their structures.

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