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

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

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

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

<p>DNA replication (B)</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 (D)</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 (C)</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 (C)</p> Signup and view all the answers

What is the shape of a bacterial chromosome?

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

Where are eukaryotic chromosomes located?

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

What is the function of histone H1?

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

What is the structure of a nucleosome?

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

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

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

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

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

What is the purpose of histone modification in chromatin structure?

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

What is the shape of the E. coli chromosome?

<p>Circular (D)</p> Signup and view all the answers

How many origins of replication do eukaryotic chromosomes have?

<p>Several (A)</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 (C)</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 (B)</p> Signup and view all the answers

What is the direction of nucleotide addition by DNA polymerases?

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

What is the purpose of topoisomerase during DNA replication?

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

What is the role of primase in DNA replication?

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

What is the direction of DNA synthesis by DNA polymerase?

<p>5’-3’ (B)</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 (D)</p> Signup and view all the answers

What is the difference between dATP and ATP?

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

What is the function of DNA ligase in DNA replication?

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

What is the direction of leading strand synthesis?

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

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

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

What is the role of primase during DNA replication?

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

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

<p>5'→3' (D)</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 (D)</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 (C)</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 (A)</p> Signup and view all the answers

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

<p>5'→3' (C)</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 (B)</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 (B)</p> Signup and view all the answers

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

<p>Heterochromatin (D)</p> Signup and view all the answers

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

<p>Interphase (C)</p> Signup and view all the answers

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

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

What is the structure of a nucleosome?

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

What is the purpose of nucleosomes in chromatin structure?

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

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

<p>Nucleosomes (D)</p> Signup and view all the answers

What is the type of sugar found in DNA nucleotides?

<p>Deoxyribose (D)</p> Signup and view all the answers

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

<p>Hydrogen bond (B)</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’ (B)</p> Signup and view all the answers

What is the purpose of the nitrogenous bases in DNA?

<p>To encode hereditary information (D)</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 (A)</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 (B)</p> Signup and view all the answers

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

<p>Double helix (D)</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 (C)</p> Signup and view all the answers

What is the primary function of DNA polymerases during replication?

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

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

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

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

<p>To correct errors during DNA replication (D)</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 (B)</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 (A)</p> Signup and view all the answers

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

<p>3'→5' (A)</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 (C)</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 (D)</p> Signup and view all the answers

What is the main consequence of Xeroderma pigmentosum?

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

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

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

Which repair mechanism is responsible for repairing thymine dimers?

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

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

<p>Mismatched bases (C)</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) (B)</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 (C)</p> Signup and view all the answers

Which type of DNA damage is caused by chemicals?

<p>Chemical modification of bases (D)</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. (C)</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. (D)</p> Signup and view all the answers

How many origins of replication can a eukaryotic chromosome have?

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

What is the direction of replication from each origin?

<p>Bidirectional. (B)</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. (D)</p> Signup and view all the answers

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

<p>A replication bubble forms. (B)</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. (B)</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. (C)</p> Signup and view all the answers

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