Evidence for DNA as Genetic Material
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Questions and Answers

What process describes the change in genotype and phenotype due to the assimilation of external DNA by a cell?

  • Conjugation
  • Mutation
  • Transformation (correct)
  • Transduction

    • Which scientist provided evidence that DNA is the genetic material in phages through radioactive tagging?

  • T.H. Morgan
  • Alfred Hershey and Martha Chase (correct)
  • Frederick Griffith
  • Erwin Chargaff

    • According to Chargaff's Rules, what relationship exists between the number of adenines and thymines in DNA?

  • Thymine exceeds adenine.
  • They are approximately equal. (correct)
  • Adenine exceeds thymine.
  • They are unequal in number.

    • What type of virus specifically infects bacteria?

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

    What is the role of the capsid in a virus?

    <p>It protects the viral RNA or DNA.</p> Signup and view all the answers

    What results from the union of gametes?

    <p>A zygote</p> Signup and view all the answers

    What type of reproduction produces offspring that are genetic copies of the parent?

    <p>Asexual reproduction</p> Signup and view all the answers

    What process do sporophytes undergo to form spores?

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

    How many chromosomes are present in each somatic cell of humans?

    <p>46</p> Signup and view all the answers

    What is the role of homologous chromosomes in genetics?

    <p>They have the same length and centromere position.</p> Signup and view all the answers

    What type of cells can undergo meiosis?

    <p>Only diploid cells</p> Signup and view all the answers

    How many daughter cells are produced at the end of meiosis?

    <p>4</p> Signup and view all the answers

    What occurs during the interphase before meiosis?

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

    What is a point mutation in genetics?

    <p>It is a change in a single nucleotide pair of a gene.</p> Signup and view all the answers

    What type of mutation can convert a codon for an amino acid into a stop codon?

    <p>Nonsense Mutation</p> Signup and view all the answers

    Which process requires protein factors to aid in the translation of a polypeptide?

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

    What is the result of nucleotide-pair insertions or deletions in a gene?

    <p>Frameshift mutations that alter the reading frame.</p> Signup and view all the answers

    What is the primary role of the CRISPR-Cas9 system?

    <p>To serve as a natural virus defense in bacteria.</p> Signup and view all the answers

    What event can cause new mutations to arise?

    <p>Errors during DNA replication.</p> Signup and view all the answers

    Which of the following types of small-scale mutations does NOT result in a change in amino acid sequence?

    <p>Silent Mutation</p> Signup and view all the answers

    What happens during the elongation phase of polypeptide synthesis?

    <p>Amino acids are sequentially added to the polypeptide chain.</p> Signup and view all the answers

    What type of mutation is known to replace one nucleotide and its partner with another pair of nucleotides?

    <p>Substitution Mutation</p> Signup and view all the answers

    What is the significance of the small ribosomal subunit during the initiation of translation?

    <p>It base-pairs with mRNA to start translation.</p> Signup and view all the answers

    What is the primary difference between the cells produced by meiosis and those produced by mitosis?

    <p>Meiosis results in four cells, while mitosis produces two cells.</p> Signup and view all the answers

    What occurs during prophase I of meiosis that is not seen in mitosis?

    <p>Homologous chromosomes undergo synapsis.</p> Signup and view all the answers

    How does independent assortment contribute to genetic variation?

    <p>It randomizes the separation of maternal and paternal chromosomes.</p> Signup and view all the answers

    What results from crossing over during prophase I of meiosis?

    <p>The production of recombinant chromosomes.</p> Signup and view all the answers

    During which phase of meiosis do sister chromatids separate?

    <p>Anaphase II</p> Signup and view all the answers

    What is the significance of the synaptonemal complex during meiosis?

    <p>It aids in the attachment of homologous chromosomes.</p> Signup and view all the answers

    Which statement about meiosis is true?

    <p>Meiosis leads to genetic diversity in gametes.</p> Signup and view all the answers

    What characterizes the cells formed at the end of meiosis II?

    <p>They are haploid and genetically distinct from each other.</p> Signup and view all the answers

    What is the role of random fertilization in genetic variation?

    <p>It adds variety to the genetic makeup of offspring.</p> Signup and view all the answers

    Which phase of meiosis involves the alignment of homologous chromosomes at the metaphase plate?

    <p>Metaphase I</p> Signup and view all the answers

    What is the function of the centromere during cell division?

    <p>It holds sister chromatids together</p> Signup and view all the answers

    What occurs during the G1 phase of interphase?

    <p>Cell undergoes significant growth</p> Signup and view all the answers

    Which of the following describes the process of cytokinesis?

    <p>Formation of a cleavage furrow</p> Signup and view all the answers

    What is the role of cyclins in the cell cycle?

    <p>To regulate checkpoints</p> Signup and view all the answers

    Which stage of mitosis is characterized by chromosomes aligning at the metaphase plate?

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

    What characterizes a malignant tumor?

    <p>It can metastasize to distant sites</p> Signup and view all the answers

    What happens during the anaphase phase of mitosis?

    <p>Sister chromatids are separated</p> Signup and view all the answers

    What is the significance of the G0 phase in the cell cycle?

    <p>Cells are metabolically inactive</p> Signup and view all the answers

    What type of cell division occurs in prokaryotes?

    <p>Binary fission</p> Signup and view all the answers

    During which phase does the mitotic spindle begin to form?

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

    What is the defined role of a checkpoint in the cell cycle?

    <p>To regulate progress through the cycle</p> Signup and view all the answers

    Which structure is not essential for cell division but is involved in forming the mitotic spindle?

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

    What happens at the G2 checkpoint?

    <p>Cells with damaged DNA are prevented from dividing</p> Signup and view all the answers

    Which of the following is a characteristic of somatic cells?

    <p>They contain 46 chromosomes in humans</p> Signup and view all the answers

    Which hypothesis suggests that genes dictate phenotypes through the production of enzymes?

    <p>One gene–one enzyme hypothesis</p> Signup and view all the answers

    What is the correct sequence of steps in DNA replication as described?

    <p>Unwinding, binding, synthesizing, proofreading</p> Signup and view all the answers

    Which of the following is a function of the poly-A tail added to mRNA?

    <p>Facilitate ribosome binding</p> Signup and view all the answers

    What key feature distinguishes the leading strand from the lagging strand during DNA replication?

    <p>Direction of synthesis</p> Signup and view all the answers

    Which type of enzyme is responsible for adding new nucleotides during DNA replication?

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

    What is the primary function of single-strand binding proteins during DNA replication?

    <p>To prevent DNA strands from re-pairing</p> Signup and view all the answers

    In which form of chromatin is DNA more densely packed?

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

    During transcription in eukaryotic cells, which RNA polymerase is primarily responsible for synthesizing mRNA?

    <p>RNA polymerase II</p> Signup and view all the answers

    What does Chargaff's rule state about the nucleotide composition of DNA?

    <p>The number of adenines equals the number of thymines</p> Signup and view all the answers

    What is the significance of telomeres in eukaryotic chromosomes?

    <p>They protect chromosomes from degradation</p> Signup and view all the answers

    Which structure is created by the binding of histones to DNA?

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

    What is the function of a replication fork during DNA replication?

    <p>To indicate the direction of DNA synthesis</p> Signup and view all the answers

    How is RNA synthesized in relation to the DNA template strand?

    <p>In an antiparallel direction</p> Signup and view all the answers

    Study Notes

    Evidence for DNA as Genetic Material

    • Morgan's Group: Genes are part of chromosomes, composed of DNA and protein.

    Griffith's Experiment (1928)

    • Pneumonia Bacteria: Studied Streptococcus pneumoniae, a bacterium causing pneumonia.
    • Transformation: Mixed pathogenic (disease-causing) and non-pathogenic (harmless) bacteria strains. Some non-pathogenic cells transformed into pathogenic ones, inheritable by their descendants. This demonstrated a change in genotype and phenotype from acquiring external DNA.

    Bacteriophages and Viruses

    • Bacteriophages: Viruses infecting bacteria, composed of DNA (or RNA) and a protein coat (capsid). They must invade a cell for replication.

    Hershey-Chase Experiment

    • T2 Bacteriophage: Studied T2, a phage infecting Escherichia coli
    • Radioactive Isotopes: Used radioactive sulfur to tag protein and radioactive phosphorus to tag DNA.
    • DNA as Genetic Material: Concluded that DNA, not protein, is the genetic material of the phage.

    Chargaff's Studies

    • Nucleotides: DNA is a polymer of nucleotides, each with a nitrogenous base, deoxyribose sugar, and a phosphate group.
    • Nitrogenous Bases: Bases include adenine (A), thymine (T), guanine (G), and cytosine (C).
    • Molecular Diversity: DNA base composition (A, T, G, C percentages) varies among species.
    • Base Pairing: Observed that the number of adenine bases roughly equals thymine, and the number of guanine bases roughly equals cytosine.

    Chargaff's Rules

    • Species Variation: DNA base composition varies between different species.
    • Base Equality: Within a species, the percentages of adenine and thymine bases are roughly equal, and the percentages of guanine and cytosine bases are roughly equal.

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    Cell Division to DNA Replication PDF Lecture Notes

    Description

    Explore the pivotal experiments and evidence demonstrating that DNA is the genetic material. This quiz covers key studies such as Griffith's experiment, the Hershey-Chase experiment, and the role of bacteriophages. Test your knowledge and understanding of the foundational concepts in genetics.

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