Molecular Basis of Inheritance
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Questions and Answers

What was the major challenge to biologists in the 20th century?

  • To study the behavior of chromosomes
  • To identify the molecules of inheritance (correct)
  • To understand the process of protein synthesis
  • To understand the structure of DNA

    • What were the two components of chromosomes that were candidates for the genetic material?

  • Nucleotides and amino acids
  • Lipids and carbohydrates
  • DNA and protein (correct)
  • RNA and protein

    • What was the initial reason why protein was a stronger candidate than DNA for the genetic material?

  • Protein was more easily visible under a microscope
  • Protein was more abundant in cells
  • Protein was seen as more complex and likely to contain genetic information (correct)
  • Protein was easier to isolate

    • What characteristics did the genetic material need to have?

    <p>Be easy to copy, be variable, and contain information</p> Signup and view all the answers

    Which organisms were studied to first discover the role of DNA in heredity?

    <p>Bacteria and viruses</p> Signup and view all the answers

    What is the process of creating a copy of DNA called?

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

    What is the name of the scientists who contributed to the discovery of the structure of DNA?

    <p>Watson and Crick</p> Signup and view all the answers

    What is the name of the chapter in Campbell Biology that discusses DNA structure and function?

    <p>Chapter 16</p> Signup and view all the answers

    What is the result of a condensation reaction in DNA synthesis?

    <p>A molecule of water is excluded</p> Signup and view all the answers

    What is the shape of a bacterial chromosome?

    <p>Circular double-stranded</p> Signup and view all the answers

    Where are eukaryotic chromosomes located?

    <p>In the nucleus</p> Signup and view all the answers

    What is the function of histone H1?

    <p>To stabilize the interaction between DNA and nucleosomal histones</p> Signup and view all the answers

    What is the structure of a nucleosome?

    <p>8 histone molecules and 168 base pairs of DNA</p> Signup and view all the answers

    What is the term for loosely packed chromatin that enables gene expression?

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

    During which stage of the cell cycle is chromatin highly condensed?

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

    What is the purpose of histone modification in chromatin structure?

    <p>To stabilize chromatin structure</p> Signup and view all the answers

    What is the shape of the E. coli chromosome?

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

    How many origins of replication do eukaryotic chromosomes have?

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

    What is the function of helicases during DNA replication?

    <p>To untwist the double helix at the replication forks</p> Signup and view all the answers

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

    <p>To bind and stabilize single-stranded DNA</p> Signup and view all the answers

    What is the direction of nucleotide addition by DNA polymerases?

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

    What is the purpose of topoisomerase during DNA replication?

    <p>To correct 'overwinding' ahead of replication forks</p> Signup and view all the answers

    What is the limitation of DNA polymerases in terms of initiation of replication?

    <p>They can only add nucleotides to a pre-existing nucleotide chain</p> Signup and view all the answers

    What is the shape of the region at the end of each replication bubble where new DNA strands are elongating?

    <p>Y-shaped</p> Signup and view all the answers

    What is the role of primase in DNA replication?

    <p>To synthesize a short RNA primer</p> Signup and view all the answers

    What is the direction of DNA synthesis by DNA polymerase?

    <p>5’-3’</p> Signup and view all the answers

    What is the purpose of the RNA primer in DNA replication?

    <p>To provide a starting point for DNA synthesis</p> Signup and view all the answers

    What is the difference between dATP and ATP?

    <p>The type of sugar they contain</p> Signup and view all the answers

    What is the function of DNA ligase in DNA replication?

    <p>To join Okazaki fragments</p> Signup and view all the answers

    What is the direction of leading strand synthesis?

    <p>5’-3’</p> Signup and view all the answers

    What is the function of the sliding clamp in DNA replication?

    <p>To hold DNA polymerase in place</p> Signup and view all the answers

    What is the result of the modified 3’-OH group in AZT?

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

    What is the role of primase during DNA replication?

    <p>To synthesize short RNA primers</p> Signup and view all the answers

    Which enzyme is responsible for adding DNA nucleotides to each primer in the 5'→3' direction?

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

    What is the direction of DNA synthesis during lagging strand synthesis?

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

    What is the purpose of DNA ligase during DNA replication?

    <p>To join DNA fragments to the subsequent Okazaki fragments</p> Signup and view all the answers

    What happens to the RNA primer after DNA pol III reaches the next RNA primer?

    <p>It is detached by DNA polymerase III</p> Signup and view all the answers

    What is the role of DNA polymerase I during DNA replication?

    <p>To replace RNA primers with DNA nucleotides</p> Signup and view all the answers

    What is the overall direction of replication during lagging strand synthesis?

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

    What is the purpose of Okazaki fragments during DNA replication?

    <p>To facilitate DNA synthesis in the 5'→3' direction</p> Signup and view all the answers

    What is the primary function of histone H1 in chromatin structure?

    <p>To stabilize the interaction between DNA and nucleosomal histones</p> Signup and view all the answers

    What is the term for the highly condensed form of chromatin that inhibits gene expression?

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

    During which stage of the cell cycle is most chromatin in a loosely packed form?

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

    What is the diameter of the 30-nm chromatin fiber?

    <p>30 nm</p> Signup and view all the answers

    What is the result of a condensation reaction in DNA synthesis?

    <p>A molecule of water is excluded</p> Signup and view all the answers

    What is the structure of a nucleosome?

    <p>Histone octamer + ds DNA</p> Signup and view all the answers

    What is the purpose of nucleosomes in chromatin structure?

    <p>To compact DNA into the nucleus</p> Signup and view all the answers

    What is the structure of the chromatin fiber that is 10 nm in diameter?

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

    What is the type of sugar found in DNA nucleotides?

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

    What is the bond that holds the two strands of DNA together?

    <p>Hydrogen bond</p> Signup and view all the answers

    What is the direction of the sugar-phosphate backbone in a DNA molecule?

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

    What is the purpose of the nitrogenous bases in DNA?

    <p>To encode hereditary information</p> Signup and view all the answers

    What is the base pairing rule described by Watson and Crick?

    <p>Adenine pairs with thymine, and guanine pairs with cytosine</p> Signup and view all the answers

    What is the term for the equal number of A and T bases, and G and C bases in any species?

    <p>Chargaff’s rule</p> Signup and view all the answers

    What is the shape of the DNA molecule described by Watson and Crick?

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

    What is the function of the phosphate group in a DNA nucleotide?

    <p>To form a phosphodiester bond with the sugar molecule</p> Signup and view all the answers

    What is the primary function of DNA polymerases during replication?

    <p>To proofread and correct mismatched nucleotides</p> Signup and view all the answers

    What type of DNA damage is caused by UV light and X-rays?

    <p>Radiation damage</p> Signup and view all the answers

    What is the primary function of mismatch repair (MMR)?

    <p>To correct errors during DNA replication</p> Signup and view all the answers

    What is the name of the process by which DNA polymerases correct mismatched nucleotides during replication?

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

    What is the term for the type of DNA lesion that is repaired by nucleotide excision repair (NER)?

    <p>Bulky helix-distorting lesions</p> Signup and view all the answers

    What is the direction of the exonuclease activity of DNA polymerases during proofreading?

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

    What is the primary function of base excision repair (BER)?

    <p>To remove small non-helix distorting DNA lesions</p> Signup and view all the answers

    What is the result of DNA polymerases' proofreading and exonuclease activity during replication?

    <p>Removal of mismatched nucleotides</p> Signup and view all the answers

    What is the main consequence of Xeroderma pigmentosum?

    <p>Increased susceptibility to skin cancers</p> Signup and view all the answers

    What is the type of DNA damage caused by UV light?

    <p>Thymine dimers</p> Signup and view all the answers

    Which repair mechanism is responsible for repairing thymine dimers?

    <p>Nucleotide excision repair (NER)</p> Signup and view all the answers

    What is the genetic disorder caused by a mutation in the genes encoding for the NER repair enzymes?

    <p>Xeroderma pigmentosum</p> Signup and view all the answers

    Which type of DNA damage is repaired by the MMR repair mechanism?

    <p>Mismatched bases</p> Signup and view all the answers

    What is the type of DNA repair mechanism that is inactive in Xeroderma pigmentosum patients?

    <p>Nucleotide excision repair (NER)</p> Signup and view all the answers

    What is the result of the inactivation of the NER repair mechanism in Xeroderma pigmentosum patients?

    <p>Increased susceptibility to skin cancers</p> Signup and view all the answers

    Which type of DNA damage is caused by chemicals?

    <p>Chemical modification of bases</p> Signup and view all the answers

    What is the result of DNA replication according to the semiconservative model?

    <p>Each daughter molecule has 1 old strand and 1 newly synthesized strand.</p> Signup and view all the answers

    What is the purpose of origins of replication in DNA replication?

    <p>To initiate the synthesis of a new strand.</p> Signup and view all the answers

    How many origins of replication can a eukaryotic chromosome have?

    <p>Hundreds or thousands.</p> Signup and view all the answers

    What is the direction of replication from each origin?

    <p>Bidirectional.</p> Signup and view all the answers

    What is the structure of the newly synthesized DNA molecule during replication?

    <p>A double helix with one old strand and one new strand.</p> Signup and view all the answers

    What is the result of the separation of DNA strands during replication?

    <p>A replication bubble forms.</p> Signup and view all the answers

    What is the significance of the semiconservative model of DNA replication?

    <p>It ensures that the genetic information is preserved during DNA replication.</p> Signup and view all the answers

    What is the characteristic of DNA replication that makes it a fast and highly accurate process?

    <p>It involves multiple enzymes and other proteins.</p> Signup and view all the answers

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