Packaging of DNA Helix and E. coli DNA
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Questions and Answers

What is the approximate length of a DNA double helix in a typical mammalian cell?

  • 10–6 m
  • 0.34 nm
  • 1.36 mm
  • 2.2 metres (correct)

    • What components primarily hold E.coli DNA in a defined region within the cell?

  • Proton carriers
  • Nucleosomes
  • Histones
  • Proteins with positive charges (correct)

    • Which amino acids are primarily found in histones that contribute to their positive charge?

  • Cysteine and Methionine
  • Tyrosine and Serine
  • Aspartic acid and Glutamic acid
  • Lysine and Arginine (correct)

    • How many base pairs does a typical nucleosome contain?

    <p>200 bp</p> Signup and view all the answers

    The beads-on-string structure observed in chromatin is mainly composed of what?

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

    What structural organization is formed when nucleosomes are further coiled and condensed during cell division?

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

    What is the primary role of histone proteins in the packaging of DNA?

    <p>To stabilize and condense DNA</p> Signup and view all the answers

    Which characteristic of DNA contributes to its organization in prokaryotes like E.coli?

    <p>Its negatively charged nature</p> Signup and view all the answers

    What is the function of the lac operon in bacteria?

    <p>It regulates the metabolism of lactose.</p> Signup and view all the answers

    What phenomenon does DNA Fingerprinting rely on?

    <p>Polymorphism in DNA sequences.</p> Signup and view all the answers

    What would happen if 20% of cytosine is present in a double-stranded DNA?

    <p>Adenine would be at 30%.</p> Signup and view all the answers

    What did Watson and Crick's hypothesis about DNA replication rely on?

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

    During the Hershey and Chase experiment, what was used to differentiate between DNA and protein?

    <p>Radioactive labeling.</p> Signup and view all the answers

    What occurs to the lac operon after lactose is added to the E. coli medium?

    <p>It is induced and then eventually shuts down.</p> Signup and view all the answers

    Which type of nucleic acid polymerase synthesizes RNA from a DNA template?

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

    Which type of DNA is specifically associated with repetitive sequences in the genome?

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

    What are Non-histone Chromosomal proteins primarily required for?

    <p>Higher-level packaging of chromatin</p> Signup and view all the answers

    Which type of chromatin is considered transcriptionally active?

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

    What was the key observation made by Frederick Griffith in his experiments?

    <p>Live R strain bacteria can transform into S strain</p> Signup and view all the answers

    Why did mice injected with heat-killed S strain bacteria remain healthy?

    <p>The heat-killing process inactivated all virulence</p> Signup and view all the answers

    What is the primary difference between S strain and R strain bacteria?

    <p>S strain has a polysaccharide coat; R strain does not</p> Signup and view all the answers

    Which scientist conducted experiments that contributed to the understanding of genetic material?

    <p>Frederick Griffith</p> Signup and view all the answers

    What observation did Griffith make upon injecting mice with a mixture of heat-killed S strain and live R strain bacteria?

    <p>Mice died, and living S strain bacteria were recovered</p> Signup and view all the answers

    What is the typical outcome for mice infected with R strain bacteria?

    <p>They remain healthy without developing pneumonia</p> Signup and view all the answers

    What was completed in May 2006 related to human chromosomes?

    <p>The sequencing of all human chromosomes</p> Signup and view all the answers

    What is the estimated total number of genes in the human genome?

    <p>30,000</p> Signup and view all the answers

    What percentage of the human genome is known to code for proteins?

    <p>2%</p> Signup and view all the answers

    Which chromosome has the most genes?

    <p>Chromosome 1</p> Signup and view all the answers

    What is a significant feature of repetitive DNA sequences in the human genome?

    <p>They are thought to have no direct coding functions.</p> Signup and view all the answers

    What percentage of nucleotide bases are exactly the same in all human beings?

    <p>99.9%</p> Signup and view all the answers

    What is the function of the ribosome during protein synthesis?

    <p>To catalyze the formation of peptide bonds</p> Signup and view all the answers

    What is the largest known human gene?

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

    What signifies the beginning and end of a translational unit in mRNA?

    <p>Start and stop codons</p> Signup and view all the answers

    Which of the following is NOT a level at which gene expression can be regulated in eukaryotes?

    <p>Post-translational level</p> Signup and view all the answers

    What is indicated by the identification of approximately 1.4 million locations of SNPs in humans?

    <p>They can assist in locating disease-associated sequences.</p> Signup and view all the answers

    What occurs during the elongation phase of protein synthesis?

    <p>The ribosome moves along the mRNA, adding amino acids</p> Signup and view all the answers

    Why are untranslated regions (UTRs) important in mRNA?

    <p>They regulate the stability and efficiency of translation</p> Signup and view all the answers

    What happens when a release factor binds to the stop codon during translation?

    <p>Translation is terminated and the polypeptide is released</p> Signup and view all the answers

    How does beta-galactosidase contribute to the metabolism of E. coli?

    <p>It catalyzes the hydrolysis of lactose into simpler sugars</p> Signup and view all the answers

    Which component of the ribosome acts as an enzyme during peptide bond formation?

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

    Study Notes

    Packaging of DNA Helix

    • DNA is a very long molecule
    • In a typical mammalian cell, the DNA helix is 2.2 meters long.
    • This is much longer than the typical nucleus, which is only about 10^-6 meters in diameter.
    • To fit inside the nucleus DNA is tightly packaged with proteins
    • In prokaryotes like E. coli, DNA is organized into large loops held by proteins in a region called the nucleoid
    • In eukaryotes, DNA is packaged with proteins called histones, positively charged proteins that are rich in lysine and arginine
    • Histones form an octamer, a unit of eight molecules around which DNA wraps to form a nucleosome
    • A typical nucleosome contains 200 base pairs of DNA
    • Nucleosomes are the repeating units of a structure called chromatin, which is visible under an electron microscope as "beads-on-a-string"
    • The chromatin fibers can be further coiled and condensed to form chromosomes during cell division

    E. coli DNA

    • E. coli DNA is 1.36 millimeters long, and has 4.0 x 10^6 base pairs.

    Chromatin Structure

    • Chromatin fibers are further coiled and condensed to form chromosomes
    • The packaging of chromatin at higher levels requires a set of proteins called nonhistone chromosomal (NHC) proteins

    Euchromatin and Heterochromatin

    • Euchromatin is loosely packed and stains lightly
    • Heterochromatin is densely packed and stains darkly
    • Euchromatin is transcriptionally active, meaning it is actively being used to produce proteins
    • Heterochromatin is inactive and is not being transcribed.

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    Description

    Explore the intricate packaging of DNA within cells, focusing on the differences between prokaryotic and eukaryotic DNA structures. Learn about histones, nucleosomes, and how chromatin condenses into chromosomes. This quiz covers key concepts regarding the organization of DNA in E. coli as well.

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