Chapter 7: DNA Structure and Replication Quiz
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Questions and Answers

What type of bond is present between adenine (A) and thymine (T) in DNA base pairing?

  • Covalent bond
  • Double bond (correct)
  • Single bond
  • Triple bond

    • How many hydrogen bonds are there between guanine (G) and cytosine (C) in DNA base pairing?

  • Three hydrogen bonds (correct)
  • Two hydrogen bonds
  • One hydrogen bond
  • Four hydrogen bonds

    • What does the direction '5'-3'' refer to in DNA strands?

  • The number of hydrogen bonds in the DNA structure
  • The position of the nitrogenous bases
  • The sugar-phosphate backbone orientation (correct)
  • The orientation of the helix

    • Which scientist/s proposed that DNA has a double helix structure?

    <p>Watson and Crick</p> Signup and view all the answers

    Rosalind Franklin's contribution to DNA involved:

    <p>X-ray diffraction data</p> Signup and view all the answers

    What was the significance of Chargaff's rules of base composition?

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

    In the Avery, MacLeod, and McCarty Experiment, what did they demonstrate about DNA?

    <p>DNA transformation in bacteria</p> Signup and view all the answers

    What was the outcome of Hershey-Chase Experiment?

    <p>'Transforming principle' was DNA</p> Signup and view all the answers

    'Base pairing' in DNA refers to the bonding between:

    <p>'Nitrogenous bases' of complementary strands</p> Signup and view all the answers

    'Antiparallel' arrangement in DNA means that:

    <p>'Both backbones have opposite orientations'</p> Signup and view all the answers

    What is the primary force responsible for base pairing in DNA?

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

    Which of the following statements about the DNA structure is incorrect?

    <p>The base pairs are arranged in a parallel manner.</p> Signup and view all the answers

    What is the significance of Griffith's Transformation Experiment in the context of DNA?

    <p>It demonstrated the transfer of genetic material between bacterial cells.</p> Signup and view all the answers

    Which of the following statements correctly describes the base pairing in DNA?

    <p>Adenine (A) pairs with Thymine (T), and Guanine (G) pairs with Cytosine (C).</p> Signup and view all the answers

    What is the significance of the '5'-3'' direction in DNA strands?

    <p>It denotes the direction of the sugar-phosphate backbone.</p> Signup and view all the answers

    Which scientist's contribution was pivotal in determining the double-helix structure of DNA?

    <p>James Watson and Francis Crick</p> Signup and view all the answers

    What was the significance of Chargaff's rules of base composition in the context of DNA structure?

    <p>It revealed that the bases in DNA are present in specific ratios.</p> Signup and view all the answers

    Which of the following statements about the Hershey-Chase Experiment is correct?

    <p>It provided evidence that DNA is the genetic material.</p> Signup and view all the answers

    What was the significance of the Avery, MacLeod, and McCarty Experiment in the context of DNA?

    <p>It demonstrated that DNA is the genetic material.</p> Signup and view all the answers

    What was Rosalind Franklin's contribution to the discovery of the DNA structure?

    <p>She provided X-ray diffraction data that revealed the helical structure of DNA.</p> Signup and view all the answers

    What did Frederick Griffith's transformation experiment with Streptococcus pneumoniae demonstrate?

    <p>Transformation of avirulent strains to virulent strains</p> Signup and view all the answers

    Which geneticists favored proteins as the genetic material in the 1940s?

    <p>Hershey and Chase</p> Signup and view all the answers

    What did Hershey and Chase's experiment using radioisotopes demonstrate?

    <p>DNA directs viral reproduction</p> Signup and view all the answers

    What do nucleotides consist of in terms of their components?

    <p>Phosphate group and pentose sugar</p> Signup and view all the answers

    Which type of bond links nucleotides in DNA during synthesis?

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

    What did Erwin Chargaff's rules of base composition establish in the field of genetics?

    <p>The ratio of pyrimidines to purines in DNA</p> Signup and view all the answers

    Which molecule must exhibit the ability to replicate, store information, express information, and allow variation by mutation to serve as genetic material?

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

    What characteristics must the genetic material exhibit according to the text?

    <p>Replication, storage of information, expression of information, mutation capability</p> Signup and view all the answers

    In 1903, Walter Sutton and Theodor Boveri described parallels between chromosome partitioning into gametes and the inheritance of genes. What does this indicate?

    <p>Genes are located on chromosomes</p> Signup and view all the answers

    Why was DNA made a candidate for the hereditary material in 1923?

    <p>Due to its localization to chromosomes and characteristics like replication and storage of information</p> Signup and view all the answers

    Why were proteins and RNA also considered to be candidates for the hereditary material?

    <p>Due to their presence in chromosomes</p> Signup and view all the answers

    What was the significance of Mendel's hereditary principles being rediscovered in 1900 according to the text?

    <p>It showed the inheritance of traits from parents</p> Signup and view all the answers

    What was the key finding from Rosalind Franklin's X-ray diffraction analysis of DNA?

    <p>DNA has a double helix structure with a periodicity of 3.4 Angstroms</p> Signup and view all the answers

    According to the Watson and Crick model, what is the arrangement of the two DNA strands?

    <p>Anti-parallel strands connected by base pairing</p> Signup and view all the answers

    What is the significance of the '5'-3'' direction in DNA strands?

    <p>It represents the polarity of the sugar-phosphate backbone</p> Signup and view all the answers

    Based on Chargaff's rules, what can be inferred about the base composition of DNA?

    <p>The amount of adenine (A) equals the amount of guanine (G), and the amount of thymine (T) equals the amount of cytosine (C)</p> Signup and view all the answers

    Which of the following statements accurately describes the base pairing in DNA?

    <p>Adenine (A) pairs with thymine (T) via two hydrogen bonds, and guanine (G) pairs with cytosine (C) via three hydrogen bonds</p> Signup and view all the answers

    What was the significance of the Hershey-Chase Experiment in relation to DNA?

    <p>It demonstrated that DNA is the genetic material that carries hereditary information</p> Signup and view all the answers

    In the DNA structure, what is the significance of the antiparallel arrangement of the two backbones?

    <p>It allows for the formation of hydrogen bonds between complementary base pairs</p> Signup and view all the answers

    What was the significance of Erwin Chargaff's rules of base composition in the context of DNA structure?

    <p>They showed that the ratio of adenine to thymine and guanine to cytosine is always equal in DNA</p> Signup and view all the answers

    Which of the following statements accurately describes the chemical affinity responsible for base pairing in DNA?

    <p>Hydrogen bonds form between complementary base pairs</p> Signup and view all the answers

    In the context of DNA structure, what is the significance of the '5'-3'' direction of the strands?

    <p>It determines the direction of DNA replication and transcription</p> Signup and view all the answers

    Which of the following experiments or observations was not directly involved in the discovery of the DNA double helix structure?

    <p>Meselson-Stahl Experiment</p> Signup and view all the answers

    Which of the following statements accurately describes the significance of the Hershey-Chase Experiment in the context of DNA structure?

    <p>It provided direct evidence that DNA is the genetic material</p> Signup and view all the answers

    Which of the following statements accurately describes the significance of the Avery, MacLeod, and McCarty Experiment in the context of DNA structure?

    <p>It provided evidence that DNA is the genetic material</p> Signup and view all the answers

    Study Notes

    DNA Structure and Function

    • Adenine (A) pairs with Thymine (T) via two hydrogen bonds, a weak chemical bond
    • Guanine (G) pairs with Cytosine (C) via three hydrogen bonds
    • '5'-3'' direction in DNA refers to the orientation of the sugar-phosphate backbone, with 5' end having a free phosphate group, and 3' end having a free hydroxyl group
    • James Watson and Francis Crick proposed the double helix structure of DNA
    • Rosalind Franklin's contribution to DNA was using X-ray diffraction to capture images that provided crucial insights into its structure
    • Chargaff's rules of base composition revealed that the amount of A always equals the amount of T and the amount of G always equals the amount of C, leading to the complementary pairing of bases in DNA
    • Avery, MacLeod, and McCarty Experiment demonstrated that DNA is the transforming principle, meaning DNA carries genetic information and can be passed down to succeeding generations
    • Hershey-Chase Experiment confirmed DNA as the genetic material by showing that DNA, not protein, is transferred from bacteriophages to bacteria, resulting in phage progeny

    DNA Base Pairing

    • Base pairing in DNA refers to the specific bonding between complementary bases (A with T, and G with C).
    • Antiparallel arrangement in DNA means the two strands run in opposite directions with 5' end of one strand aligning with the 3' end of the other strand
    • Hydrogen bonds are the primary force responsible for base pairing in DNA
    • DNA strands are antiparallel and run in opposite directions.

    DNA structure and properties

    • DNA has a double helix structure with two antiparallel strands, complementary base pairing, and a sugar-phosphate backbone holding them together
    • Griffith's Transformation Experiment was significant because it demonstrated the existence of a 'transforming principle': a substance capable of changing the characteristics of bacteria
    • '5'-3'' direction in DNA strands is essential as it dictates the direction of DNA replication and transcription
    • DNA strands are antiparallel: they run in opposite directions (5'-3' and 3'-5')
    • Chargaff's rules of base composition played a crucial role in determining the complementary base pairing in the DNA structure, providing a foundation for understanding its structure and replication

    Key experiments and discoveries

    • Hershey-Chase experiment proved that DNA, not protein, is the genetic material, by labeling phage DNA with phosphorus and phage protein with sulfur
    • Avery, MacLeod, and McCarty Experiment identified DNA as the substance that carries genetic information and acts as the transforming principle
    • Rosalind Franklin produced X-ray diffraction images of DNA, revealing its double helix structure
    • Frederick Griffith's transformation experiment with Streptococcus pneumoniae demonstrated that genetic information can be transferred from one bacterium to another.
    • Hershey and Chase's experiment using radioactive isotopes demonstrated that DNA is responsible for transmitting genetic information from one generation to the next.

    DNA Composition

    • Nucleotides are the building blocks of DNA and are comprised of:
    • A sugar molecule (deoxyribose)
    • A phosphate group
    • A nitrogenous base (adenine, guanine, cytosine, or thymine)
    • Phosphodiester bonds link nucleotides in DNA during synthesis
    • Erwin Chargaff's rules of base composition established that the amount of adenine (A) always equals the amount of thymine (T) and the amount of guanine (G) always equals the amount of cytosine (C), which plays a crucial role in DNA replication and transcription.

    Genetic Material

    • DNA serves as the genetic material due to its ability to:
    • Replicate, allowing for the transmission of genetic information
    • Store information in its base sequence
    • Express information to produce proteins and other molecules
    • Allow variation by mutation, driving evolution
    • Genetic material must be able to replicate, store information, express information, and allow variation by mutation.

    Historical Context and Significance

    • Walter Sutton and Theodor Boveri observed parallels between chromosome partitioning into gametes and inheritance of genes, providing evidence that chromosomes carry genetic material
    • DNA became a candidate for the hereditary material in 1923 due to its stable and chemically complex structure
    • Proteins and RNA were also considered as candidates for the hereditary material due to their diverse functions and ability to carry genetic information, but RNA was not considered as stable as DNA.
    • Rediscovery of Mendel's hereditary principles in 1900 revitalized research into understanding the mechanism of inheritance
    • Rosalind Franklin's key finding from X-ray diffraction analysis was the DNA structure's double helix configuration, demonstrating its shape and arrangement
    • According to the Watson and Crick model, the two DNA strands in a double helix are antiparallel and complementary, meaning that they run in opposite directions and their bases pair according to specific rules (A with T and G with C)
    • '5'-3'' direction in DNA strands is important for defining the direction of replication and transcription, essential processes within the cell
    • Chargaff's rules indicate that the proportion of adenine (A) always equals the proportion of thymine (T) and the proportion of guanine (G) always equals the proportion of cytosine (C) in a given sample of DNA
    • Base pairing in DNA involves hydrogen bonds formed between specific pairs of nitrogenous bases - adenine (A) with thymine (T), and guanine (G) with cytosine (C)
    • Hershey-Chase Experiment significantly confirmed DNA as the genetic material by demonstrating that DNA, not protein, is transferred from bacteriophages to bacteria
    • Antiparallel arrangement in DNA structure is vital for maintaining the double helix structure and allowing for proper base pairing
    • Chargaff's rules, which demonstrated the equal proportions of adenine and thymine and guanine and cytosine in DNA, were crucial for understanding complementary base pairing in DNA and its double helix structure
    • Hydrogen bonds are the primary force responsible for base pairing in DNA due to their weak and specific interactions
    • The '5'-3'' direction of DNA strands influences the direction of replication and transcription, crucial processes for maintaining genetic information
    • Griffith's transformation experiments with Streptococcus pneumoniae, Avery, MacLeod, and McCarty Experiment, and Hershey-Chase Experiment contributed significantly to the discovery of the DNA double helix structure
    • Hershey-Chase Experiment provided definitive evidence that DNA is the genetic material, confirming findings from Avery, MacLeod, and McCarty Experiment
    • Avery, MacLeod, and McCarty Experiment demonstrated that DNA is the transforming principle responsible for carrying genetic information, laying the groundwork for understanding DNA as the core molecule of life.

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