Discovery of DNA: The Molecule of Heredity
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Discovery of DNA: The Molecule of Heredity

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Questions and Answers

What did Frederick Griffith's experiments suggest about the transforming substance?

  • It was DNA that caused transformation.
  • It was not proteins since they would denature with heat. (correct)
  • It was RNA that facilitated transformation.
  • It was proteins that caused transformation.

    • Who concluded that DNA was the transforming substance in Griffith's experiments?

  • Oswald Avery (correct)
  • Frederick Griffith
  • Edwin Chargraff
  • Alfred Hershey

    • What was a significant conclusion drawn from the Hershey and Chase experiments?

  • They further supported DNA as the molecule of inheritance. (correct)
  • They identified RNA as the primary genetic material.
  • They proved that proteins are the molecules of inheritance.
  • They discovered that chromosomes are made entirely of proteins.

    • What did Edwin Chargraff's work help to demonstrate about DNA?

    <p>DNA base composition varies with species.</p> Signup and view all the answers

    What characteristic of DNA was confirmed through the research of Griffith, Avery, Hershey, and Chase?

    <p>DNA exists on chromosomes and is the molecule of inheritance.</p> Signup and view all the answers

    What type of molecule are adenine and guanine classified as?

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

    What structures do pyrimidines consist of?

    <p>A four-carbon ring connected by nitrogen</p> Signup and view all the answers

    How do adenine and thymine bond in DNA structure?

    <p>Through double hydrogen bonds</p> Signup and view all the answers

    In the context of DNA, what does antiparallel mean?

    <p>Strands have opposite directionality</p> Signup and view all the answers

    Which direction does the DNA template strand run?

    <p>3' to 5'</p> Signup and view all the answers

    What shape does DNA adopt?

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

    What term describes the method of DNA replication that was confirmed by the Meselson and Stahl experiment?

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

    Which pairs of bases are correctly matched in DNA pairing?

    <p>Adenine - Thymine</p> Signup and view all the answers

    Which statement accurately describes Chargaff's findings regarding DNA?

    <p>The amount of adenine equals the amount of thymine.</p> Signup and view all the answers

    What major contribution did Wilkins and Franklin make to the understanding of DNA?

    <p>They used X-ray diffraction to reveal its helical nature.</p> Signup and view all the answers

    Which of the following was a key conclusion made by Watson and Crick about DNA?

    <p>DNA's structure allows for a copying mechanism.</p> Signup and view all the answers

    What are the three components of a nucleotide?

    <p>Phosphate group, sugar, nitrogenous base</p> Signup and view all the answers

    Which statement accurately describes polynucleotides?

    <p>They are polymers made from multiple nucleotides.</p> Signup and view all the answers

    What distinguishes a DNA nucleotide from an RNA nucleotide?

    <p>DNA nucleotides contain deoxyribose sugar.</p> Signup and view all the answers

    Which of the following nitrogenous bases is NOT found in DNA?

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

    What was the significance of the Nobel Prize awarded in 1962 related to DNA?

    <p>It honored the discoveries about the molecular structure of nucleic acids.</p> Signup and view all the answers

    What is one of the main functions of genetic information?

    <p>To enable growth, development, and function of an organism</p> Signup and view all the answers

    Which scientist is known for proposing the theory of natural selection?

    <p>Charles Darwin</p> Signup and view all the answers

    What did Mendel identify about heritable characters in his experiments?

    <p>They could be masked in the F1 generation.</p> Signup and view all the answers

    What did Johann Friedrich Miescher first isolate from the nucleus?

    <p>Nuclein, which later became known as DNA</p> Signup and view all the answers

    Which component did Albrecht Kossel identify in nuclein?

    <p>Five nitrogenous bases</p> Signup and view all the answers

    What was one of the key findings from Thomas Hunt Morgan's experiments with Drosophila melanogaster?

    <p>Eye color was linked to sex chromosomes.</p> Signup and view all the answers

    What was a limitation of Darwin's theory as it relates to inheritance?

    <p>He had no explanation for the mechanisms behind inheritance.</p> Signup and view all the answers

    In Morgan's observation of Drosophila, what ratio of red to white eye color was seen in the F2 generation?

    <p>3:1</p> Signup and view all the answers

    What type of experiments did Gregor Mendel conduct?

    <p>Plant breeding experiments</p> Signup and view all the answers

    Which of the following was a key development in the understanding of genetic inheritance?

    <p>Isolation of DNA by Miescher</p> Signup and view all the answers

    Study Notes

    Discovery of DNA: The Molecule of Heredity

    • Charles Darwin proposed evolution from a common ancestor with natural selection as the driving force. However, he lacked an explanation for inheritance.
    • Gregor Mendel's research focused on pea plants, identifying heritable characteristics masked in the first generation and predicting different character ratios later on. These "factors" were later termed as genes.
    • Johann Friedrich Miescher isolated "nuclein" – DNA and proteins – in 1869 from the nucleus, containing phosphorus and nitrogen in a unique ratio.
    • Albrecht Kossel identified the five nuclein components: Adenine, Cytosine, Guanine, Thymine, and Uracil, and coined the term "Deoxyribonucleic acid" (DNA).
    • Thomas Hunt Morgan's observations on Drosophila melanogaster (fruit flies) demonstrated the inheritance of eye color, following Mendelian principles with a 3:1 ratio (red:white) in the F2 generation.
    • Morgan's experiments revealed that all F2 females had red eyes, while males showed a 50% red and 50% white eye distribution, further supporting the link between chromosomes and inheritance.
    • Frederick Griffith's research with Streptococcus pneumoniae strains demonstrated the transformative nature of genetic material, suggesting it wasn't protein due to heat denaturing.
    • Oswald Avery confirmed DNA as the transformative substance.
    • Alfred Hershey and Martha Chase further solidified DNA as the inheritance molecule through experiments with bacteriophages.
    • Edwin Chargraff's work showed that: a) DNA base composition varies across species, indicating it wasn't a tetranucleotide with equal proportions of bases, and b) the amount of A = T and G = C (Chargaff's rules).
    • Maurice Wilkins and Rosalind Franklin utilized X-ray diffraction to demonstrate DNA's structure as a long helical rod with a diameter of 2 nm and structural regularity at 0.34 nm and 3.4 nm intervals.
    • James Watson and Francis Crick, using existing data, proposed the double helix structure of DNA, a groundbreaking discovery published in Nature in 1953.
    • Watson and Crick received the Nobel Prize in Physiology or Medicine in 1962, along with Maurice Wilkins.

    Nucleic Acids and their Structure

    • Nucleic acids like DNA are polymers composed of repeating subcomponents called nucleotides.
    • A nucleotide consists of a phosphate group, a sugar (deoxyribose in DNA), and a nitrogenous base.
    • The phosphate group connects nucleotides via phosphodiester bonds, forming the backbone of polynucleotides.
    • The sugar links the phosphate backbone to the base.
    • The nitrogenous base determines the specific nucleotide (Guanine, Thymine, Adenine, Cytosine).
    • Adenine and Guanine are purines, characterized by a double ring structure with a pyrimidine ring connected to an imidazole ring.
    • Cytosine and Thymine are pyrimidines, consisting of a single 4-carbon ring with nitrogen atoms at positions 1 and 3.
    • Adenine pairs with Thymine, and Guanine pairs with Cytosine.

    DNA Structure and Replication

    • DNA has directionality, with one strand running from 5' to 3' and the complementary strand running 3' to 5' in the opposite direction.
    • The two strands are antiparallel, meaning they run in opposite directions.
    • The base sequence on one strand dictates the complementary sequence on the other, ensuring a consistent structure.
    • The double-helix model depicts the two DNA strands intertwined, forming a helical structure.
    • The helix has a major groove and a minor groove.
    • DNA replication is a semi-conservative process, resulting in two new DNA molecules, each containing one original strand and one newly synthesized strand.
    • The Meselson and Stahl experiment provided direct experimental evidence for the semi-conservative replication of DNA.

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    BIOL1110 2022 Lecture 3 - DNA PDF

    Description

    Explore the groundbreaking discoveries that led to our understanding of DNA as the molecule of heredity. From Darwin's theories on evolution to Mendel's work with pea plants and Morgan's experiments with fruit flies, this quiz will challenge your knowledge of genetic inheritance. Dive into the history of genetics and the pivotal figures who shaped it.

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