Introduction to DNA and Genetic Information
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Questions and Answers

What is the primary goal of understanding the nature of genes?

  • To develop new treatments for pneumonia
  • To understand how information is passed from generation to generation (correct)
  • To study the effects of heat on bacteria
  • To create new strains of bacteria

    • What was Frederick Griffith studying in 1928?

  • The difference between smooth and rough colonies
  • The cause of pneumonia (correct)
  • The effect of heat on bacterial cells
  • The transformation of harmless bacteria into disease-causing bacteria

    • What was the result of injecting the S type of bacteria into mice in the control experiment?

  • The mice remained unaffected
  • The mice developed a mild infection
  • The mice survived and were healthy
  • The mice developed pneumonia and died (correct)

    • What was the outcome of Experiment 1, where heat-killed S bacteria was injected into mice?

    <p>The mice survived and were healthy</p> Signup and view all the answers

    What was the result of mixing heat-killed S bacteria with live, harmless R bacteria in Experiment 2?

    <p>The mice developed pneumonia and died</p> Signup and view all the answers

    What did Griffith conclude was the mechanism by which the harmless bacteria was transformed into a disease-causing form?

    <p>A chemical factor transferred from the heat-killed S bacteria to the live R bacteria</p> Signup and view all the answers

    What is the term used to describe the process by which one type of bacteria is changed permanently into another type?

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

    What is the characteristic of the colonies formed by the disease-causing S strain of bacteria?

    <p>They have smooth edges</p> Signup and view all the answers

    What was the main goal of Avery's experiment?

    <p>To identify the molecule responsible for bacterial transformation</p> Signup and view all the answers

    What was the result of Hershey and Chase's experiment?

    <p>They confirmed that DNA is the genetic material</p> Signup and view all the answers

    What is the main function of DNA in a cell?

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

    What is the composition of DNA?

    <p>Nucleotides joined by covalent bonds</p> Signup and view all the answers

    What is the role of Erwin Chargaff's rule?

    <p>To determine the percentage of A-T and C-G bases in DNA</p> Signup and view all the answers

    What is the characteristic of the double helix model?

    <p>Both strands run in opposite directions</p> Signup and view all the answers

    What is the function of hydrogen bonding in DNA?

    <p>To hold the nitrogenous bases together</p> Signup and view all the answers

    What did Rosalind Franklin's X-ray diffraction pattern reveal about DNA?

    <p>The strands of DNA are twisted around each other</p> Signup and view all the answers

    What is the process of DNA replication?

    <p>The process of creating a new DNA molecule by pairing one base on one strand with one base on the opposite strand</p> Signup and view all the answers

    What is the result of DNA replication?

    <p>Two identical DNA molecules with one old and one new strand</p> Signup and view all the answers

    Study Notes

    Introduction to DNA

    • Understanding DNA is crucial to understand how genetic information is passed from one generation to the next
    • Scientists needed to understand the nature of genes to determine how a cell becomes a specific organism (e.g., a mouse or a moose)

    Bacterial Transformation

    • Frederick Griffith discovered transformation in 1928 while studying bacteria that cause pneumonia
    • He isolated two types of bacteria: disease-causing (S) and harmless (R) strains
    • S strain produced smooth colonies, while R strain produced colonies with rough edges

    Griffith's Experiment

    • Injecting S type bacteria into mice resulted in death and pneumonia
    • Injecting R type bacteria into mice resulted in survival and no pneumonia
    • Mixing heat-killed S bacteria with live R bacteria and injecting into mice resulted in death and pneumonia

    Transformation

    • Griffith's experiment showed that a chemical factor transferred from heat-killed S bacteria to live R bacteria, changing the R bacteria permanently
    • This process is called transformation

    Avery's Experiment

    • Dr. Avery repeated Griffith's experiment to determine which molecule was responsible for transformation
    • He used enzymes to destroy different molecules and found that DNA was responsible for transformation

    DNA as Genetic Material

    • By observing bacterial transformation, Avery and other scientists discovered that DNA stores and transmits genetic information from one generation to the next
    • Hershey and Chase confirmed Avery's results, showing that DNA is the genetic material found in genes, not just in viruses and bacteria, but in all living cells

    Structure of DNA

    • DNA is a nucleic acid made up of nucleotides joined into long strands or chains by covalent bonds
    • Contains 4 nitrogenous bases: Adenine (A), Cytosine (C), Guanine (G), and Thymine (T)
    • Contains a 5-Carbon sugar called Deoxyribose

    Chargaff's Rule

    • Erwin Chargaff discovered that the percentage of A-T bases is equal to the percentage of C-G bases in all DNA

    Double Helix Model

    • The double helix model shows that the two strands of DNA run in opposite directions (antiparallel) with a 5' - 3' direction
    • The sides of the DNA model are comprised of Deoxyribose sugar and phosphate groups
    • The inside of the model is comprised of nitrogenous bases, with Adenine bonded with Thymine and Guanine bonded with Cytosine

    Hydrogen Bonding

    • Hydrogen bonds hold together nitrogenous bases, with A-T and C-G bonds
    • These bonds are weak and can easily separate

    Rosalind Franklin's Contribution

    • Rosalind Franklin used x-ray diffraction to study the structure of DNA
    • Her X-ray pattern showed that the strands are twisted around each other like the coils of a spring

    Watson and Crick's Model

    • Watson and Crick used Franklin's X-ray data to build a model that explained the specific structure and properties of DNA
    • Their model showed that the nitrogenous bases are stacked at regular intervals near the center of the molecule

    DNA Replication

    • DNA can be copied, with one base on one strand pairing with one base on the opposite strand
    • DNA is complementary, meaning one strand can be used to make the other strand
    • DNA replication occurs during the S phase of cell division
    • Ensures each resulting cell has the same complete set of DNA molecules

    DNA Replication Process

    • DNA is unzipped by helicase
    • Two strands are formed, with one old strand and one new strand
    • DNA polymerase joins individual nucleotides to produce a new strand of DNA and proofreads each strand
    • Resulting strands are identical and semiconservative

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    Description

    Learn about the basics of DNA, genes, and how genetic information is passed from generation to generation. Understand how bacterial transformation works and how it relates to genetic inheritance.

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