DNA as Genetic Material
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Questions and Answers

Why is variation essential for organisms?

  • It enables adaptation and evolution. (correct)
  • It simplifies the genetic structure of organisms.
  • It prevents mutations from occurring.
  • It allows organisms to maintain a constant state.

    • Friedrich Miescher initially believed nuclein to be a lipid.

    False (B)

    What are the two main components that chromosomes were found to be composed of?

    protein and nucleic acids

    Bacteriophages, such as T2, reproduce by invading a host cell like __________ and utilizing its machinery to create more viruses.

    <p>Escherichia coli</p> Signup and view all the answers

    Match the scientist with their contribution to the discovery of DNA as genetic material:

    <p>Friedrich Miescher = Discovered nucleic acid, which he called nuclein. Alfred Hershey and Martha Chase = Provided evidence that DNA is the genetic material using bacteriophages.</p> Signup and view all the answers

    Which of the following characteristics initially led scientists to believe that proteins, rather than DNA, were the primary carriers of genetic information?

    <p>Proteins are composed of 20 different amino acids, offering a greater capacity for storing information. (A)</p> Signup and view all the answers

    The Hershey-Chase experiment involved studying the T4 bacteriophage.

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

    What is the name given to the suspension of released progeny phages after a host cell ruptures?

    <p>phage lysate</p> Signup and view all the answers

    Which of the following best describes the contribution of Wilhelm Johannsen to the field of genetics?

    <p>He coined the term 'gene' and distinguished between genotype and phenotype. (D)</p> Signup and view all the answers

    Thomas Hunt Morgan's work with fruit flies supported the idea that genes are located on chromosomes.

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

    What is the primary characteristic of the lytic cycle?

    <p>Production of progeny phages and subsequent lysis of the host cell. (C)</p> Signup and view all the answers

    What was the significance of Beadle and Tatum's 'one gene, one enzyme' hypothesis?

    <p>Genes act by regulating distinct chemical events</p> Signup and view all the answers

    Hershey and Chase used radioactive isotopes of nitrogen and carbon in their experiments.

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

    The term 'gene' originates from the Greek word ________, meaning 'birth'.

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

    Why did Hershey and Chase use radioactive isotopes of phosphorus and sulfur in their experiments?

    <p>Phosphorus is only found in DNA, and sulfur is only found in proteins. (B)</p> Signup and view all the answers

    The empty outer shell of a bacteriophage that remains on the surface of the bacterium after injecting its genetic material is referred to as a phage ______.

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

    Match the following scientists with their contributions to genetics:

    <p>Wilhelm Johannsen = Coined the term 'gene' Thomas Hunt Morgan = Chromosome theory of inheritance George Beadle &amp; Edward Tatum = One gene, one enzyme hypothesis William Bateson = Coined the term 'genetics'</p> Signup and view all the answers

    A mold strain loses the ability to assemble a particular amino acid. Which of the following can support its survival?

    <p>Supplying the mold with the required amino acid in the nutrient medium. (C)</p> Signup and view all the answers

    In the Hershey-Chase experiment, which radioactive isotope was found primarily inside the bacteria after infection?

    <p>32P</p> Signup and view all the answers

    What model organism did George Beadle and Edward Tatum use to formulate the 'one gene, one enzyme' hypothesis?

    <p>Neurospora crassa (red bread mold) (B)</p> Signup and view all the answers

    What was the key conclusion from the Hershey-Chase experiment?

    <p>DNA is the genetic material. (C)</p> Signup and view all the answers

    William Astbury's X-ray diffraction patterns of crystallized DNA provided evidence for its regular structure.

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

    Genetic linkage refers to the phenomenon where genes are randomly assorted on different chromosomes.

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

    What are the three key characteristics that scientists knew the hereditary information responsible for passing traits from parent to offspring?

    <ol> <li>Contain information about an organism's cell structure, function, development, and reproduction. 2. Replicate accurately. 3. Capable of change.</li> </ol> Signup and view all the answers

    Which event directly contributed to the development of the chromosome theory of inheritance?

    <p>The study of genetic linkage and recombination in fruit flies. (D)</p> Signup and view all the answers

    What observation supported the conclusion that DNA, not protein, is the genetic material in the Hershey-Chase experiment?

    <p>Radioactively labeled DNA was found inside infected bacteria. (D)</p> Signup and view all the answers

    The differences between individual humans, such as variations in eye color and height, are primarily a result of differences in the __________ sequences that constitute the genes in their genomes.

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

    After E. coli were infected with $^{35}S$-labeled T2 phages, most of the radioactivity appeared within the cell.

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

    Match the characteristic with the corresponding requirement for genetic material:

    <p>Contain information = Must encode cell structure, function, and development. Replicate accurately = Must ensure progeny cells have the same genetic information as the parental cell. Capable of change = Must allow for adaptation and evolution over time.</p> Signup and view all the answers

    Which of the following is the most direct function of genetic information coded in DNA?

    <p>Dictating the structure, function, and development of the organism. (A)</p> Signup and view all the answers

    Before DNA and RNA were known to carry genetic information, scientists had no concept of hereditary material.

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

    A new mutation arises in a mold species, which affects its ability to produce an essential amino acid. Suggest two strategies to ensure its survival under laboratory conditions.

    <p>Supply the required amino acid in the nutrient medium; Provide precursor compounds that the cells can convert into the required amino acid.</p> Signup and view all the answers

    Signup and view all the answers

    Flashcards

    Gene (1909)

    A term coined by Wilhelm Johannsen for Mendelian units of heredity.

    Phenotype

    The observable physical appearance of an organism influenced by its genotype.

    Genotype

    The genetic makeup of an organism that determines its traits.

    Chromosome Theory (1911)

    Theory that genes are located on chromosomes and are units of heredity.

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    Drosophila melanogaster

    A model organism used in genetic studies, commonly known as the fruit fly.

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    One Gene, One Enzyme (1941)

    Hypothesis stating that a gene regulates a specific enzyme.

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    George Beadle and Edward Tatum

    Scientists who established the One Gene, One Enzyme hypothesis through experiments on Neurospora.

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    Neurospora crassa

    A red bread mold used by Beadle and Tatum to study genes and enzymes.

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    X-ray Diffraction of DNA

    The first X-ray diffraction pattern of DNA was obtained by William Astbury in 1943, revealing its structural properties.

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    Amino Acids and Mold

    Some mutations in mold affect its ability to synthesize amino acids, requiring external sources for survival.

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    Genetic Variation

    Variation among individuals in a species arises mainly from differences in DNA sequences.

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    Key Characteristics of Genetic Material

    Genetic material must provide stable information, replicate accurately, and be capable of change.

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    DNA and RNA

    DNA and RNA are molecular structures that carry and transmit genetic information across generations.

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    Stable Form of Genetic Information

    Genetic material must exist in a stable form to encode an organism's structure and function.

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    Replication of Genetic Information

    Genetic information must replicate accurately to ensure progeny cells inherit the correct data.

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    Change in Genetic Material

    Genetic material must be capable of change to allow for evolution and adaptation.

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    Friedrich Miescher

    Swiss biochemist who discovered nucleic acid in 1869.

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    Nuclein

    Substance isolated by Miescher, later known as nucleic acids.

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    Chromosomes

    Threadlike structures in nuclei that carry genetic information.

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    Proteins as genetic material

    Early belief that proteins were the carriers of genetic information.

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    DNA

    Molecule identified as genetic material; consists of four nucleotides.

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    Hershey and Chase experiment

    1953 experiment proving DNA is the genetic material using T2 bacteriophage.

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    Bacteriophage

    A virus that attacks bacteria, such as T2 in the Hershey and Chase experiment.

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    Phage lysate

    Suspension of released progeny phages after bacteria rupture.

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    Lytic Cycle

    The process in which a phage infects a bacterial cell and produces new phages that are released after the bacterium is destroyed.

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    T2 Phage

    A simple virus that infects E. coli, composed only of DNA and protein.

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    Phage Ghost

    The empty outer shell of a phage that remains on the bacterial surface after injection of genetic material.

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    Radioactive Isotopes in Media

    Radioactive forms of phosphorus and sulfur used to trace genetic material in Hershey and Chase's experiment.

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    E. coli

    A type of bacteria used in scientific experiments, including Hershey and Chase's.

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    Progeny Phages

    New phages produced by an infected bacterium after the lytic cycle.

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    32P and 35S

    Radioactive isotopes of phosphorus and sulfur, used to label DNA and protein, respectively.

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    Study Notes

    Bacterial Genetics

    • This course covers bacterial genetics, focusing on the discovery of genetic material, different types of nucleic acids, DNA replication in prokaryotes, DNA mutations, and techniques for transferring genetic information.

    Course Outcomes

    • Students will learn about experiments related to the discovery of genetic material.
    • They will study different types of nucleic acids.
    • Students will understand the DNA replication process in prokaryotes.
    • Understanding the different types of mutations in DNA is also important.
    • The course provides basic knowledge on transferring genetic information.

    Credit I - Topics

    Experimental Evidences suggesting Nucleic Acid as Genetic Material

    • Discovery of transforming material (hereditary material)
    • Griffiths experiment
    • Avery and Macleod experiment
    • Harshey and Chase experiment
    • Frankel-Conrat and Singer experiment (TMV virus)
    • Required properties of the genetic material

    Types of Nucleic Acids

    • DNA and RNA
    • Structure of DNA
      • Nitrogen bases
      • Nucleotides
      • Nucleosides
      • Polunucleotide chains
      • Bonds involved in DNA structure
      • Different forms of DNA structure

    Prokaryotic DNA Replication

    • Models of DNA replication (conservative, semi-conservative, and dispersive)
    • Meselson and Stahl experiment (semi-conservative)
    • Enzymes, proteins, and factors involved in replication
    • Steps involved in DNA replication
    • Models of DNA replication (rolling circle, theta, and linear)
    • D-loop model

    Termination of Replication

    Plasmid Genetics

    • Types of plasmids
    • Properties of plasmids
    • Plasmid replication

    Mutation and Reversions

    • Types of mutations (nonsense, missense, silent, conditional lethal, temperature -sensitive, amber, reverse, suppressor)
    • Spontaneous mutation
    • Discovery of spontaneous mutations
    • Mechanism of spontaneous mutation
    • Concept of mutagenic agents
    • Physical mutagenic agents (UV/X-ray)
    • Chemical mutagenic agents (acridine orange and EtBr)
    • Detection and isolation of mutants

    Additional Milestones

    1909: The Word Gene Coined

    • Wilhelm Johannsen coined the term "gene" to describe Mendelian units of heredity.
    • Disambiguation between phenotype and genotype was also established.
    • William Bateson also used the term "genetics" earlier to describe the topic.

    1911: Fruit Flies Illuminate the Chromosome Theory

    • Thomas Hunt Morgan and his students utilized fruit flies to study genes and chromosomes.
    • They found that genes are located on chromosomes, and their linear arrangement impacts inheritance.
    • They discovered genetic linkage and chromosome recombination.

    1940's 1941: One Gene, One Enzyme

    • George Beadle and Edward Tatum investigated the red bread mold (Neurospora crassa).
    • Their work suggested a relationship between genes and enzymatic processes (one gene, one enzyme).

    1943: X-ray Diffraction of DNA

    • William Astbury obtained the first X-ray diffraction pattern of DNA.
    • These patterns revealed that DNA has a regular structure, with nucleotide bases stacked.

    Additional Notes about Bacterial Genetics

    • Living organisms possess a genetic material responsible for heredity, that passes from parent to offspring.
    • This genetic material should have the ability to maintain information, replicate properly, and undergo changes.
    • Experiments showed that chromosomes are composed of proteins and nucleic acids (including DNA and RNA).
    • Scientists initially thought protein was the genetic material due to its complexity.
    • DNA was identified as the genetic material in bacteria and viruses.
    • Hershey and Chase used radioactive isotopes in bacteria and viruses, to prove DNA is the genetic material.

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    Related Documents

    Bacterial Genetics PDF

    Description

    Questions cover the discovery of DNA as genetic material, including key experiments and scientists involved. Topics include Miescher's discovery of nuclein, the composition of chromosomes, bacteriophage reproduction, the Hershey-Chase experiment, and the lytic cycle.

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