DNA Structure and Replication Quiz
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Questions and Answers

What is the primary function of DNA polymerase I during DNA replication?

  • Removes RNA primers and replaces them with DNA (correct)
  • Seals gaps between Okazaki fragments
  • Synthesizes RNA primers for lagging strand
  • Unwinds the DNA double helix

    • Which of the following correctly describes the role of topoisomerase during DNA replication?

  • Extends RNA primers with DNA
  • Synthesizes RNA primers
  • Relieves supercoiling tension (correct)
  • Prevents degradation of single-stranded DNA

    • What key feature is characteristic of the replication bubble in prokaryotes like E. coli?

  • Presence of multiple origins of replication
  • Inward movement of replication forks from the edges
  • A complex of primase and ligase at the replication fork
  • Formation of leading and lagging strands simultaneously from a single site (correct)

    • What role does telomerase play in relation to telomeres?

    <p>It extends telomeres by adding DNA sequences</p> Signup and view all the answers

    How does the function of DNA ligase contribute to DNA replication?

    <p>It forms phosphodiester bonds to seal gaps between Okazaki fragments</p> Signup and view all the answers

    What critical issue arises at the ends of chromosomes during DNA replication?

    <p>Loss of telomeric DNA with each replication cycle</p> Signup and view all the answers

    Which protein is responsible for binding to single-stranded DNA to prevent it from rejoining during replication?

    <p>Single-strand binding protein (SSB)</p> Signup and view all the answers

    During the S phase, which process is initiated to begin DNA replication in eukaryotic cells?

    <p>Unwinding of DNA wrapped around histones</p> Signup and view all the answers

    What role does TFIIH play during the initiation stage of transcription?

    <p>It phosphorylates RNA polymerase II for activation.</p> Signup and view all the answers

    Which of the following sequences is conserved at the 5' splice donor site?

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

    During the splicing mechanism, what initiates the first step of transesterification?

    <p>The 2’-OH of branch point A.</p> Signup and view all the answers

    Which component is NOT part of the spliceosome?

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

    What occurs during the elongation phase of transcription?

    <p>Phosphorylation of the C-terminal domain of RNA polymerase II.</p> Signup and view all the answers

    What is the primary function of introns in eukaryotic genes?

    <p>They provide regulatory roles and can form silencing RNAs.</p> Signup and view all the answers

    Which statement correctly describes the termination of transcription?

    <p>The torpedo model involves the use of exonucleases.</p> Signup and view all the answers

    What is the role of NELF during the pausing stage of transcription?

    <p>It regulates the transcription in response to cellular stress.</p> Signup and view all the answers

    What role do chaperones play in protein folding?

    <p>They assist proteins to fold correctly.</p> Signup and view all the answers

    Which of the following processes is involved in the activation of inactive pre-proteins?

    <p>Protease cleavage</p> Signup and view all the answers

    What is the primary function of ubiquitination in protein regulation?

    <p>To target proteins for degradation.</p> Signup and view all the answers

    How do nuclear localization signals (NLS) function in protein transport?

    <p>They are recognized by cytoplasmic receptor proteins.</p> Signup and view all the answers

    Which mechanism is responsible for targeting proteins to membranes or organelles?

    <p>Hydrophobic signal sequence</p> Signup and view all the answers

    What happens to the signal sequence of a protein after it is transported into the ER?

    <p>It is cleaved by peptidase.</p> Signup and view all the answers

    Which component plays a crucial role in regulating mRNA stability and translation?

    <p>Poly A binding proteins</p> Signup and view all the answers

    What is the fate of proteins packaged into lipid vesicles in the Golgi apparatus?

    <p>They are secreted extracellularly.</p> Signup and view all the answers

    What is the significance of Chargaff's Rules of Base Pairing in relation to DNA structure?

    <p>They confirm that DNA is double-stranded and complementary.</p> Signup and view all the answers

    Which component of DNA is primarily responsible for its anti-parallel strand orientation?

    <p>The arrangement of the sugar-phosphate backbone.</p> Signup and view all the answers

    How do purine and pyrimidine bases contribute to the stability of the DNA double helix?

    <p>Through hydrophobic interactions between stacked bases.</p> Signup and view all the answers

    Which type of DNA replication model maintains the original DNA strands intact?

    <p>Conservative Replication</p> Signup and view all the answers

    What was concluded from Meselson and Stahl's experiment using cesium chloride centrifugation?

    <p>First generation DNA contains a mix of heavy and light strands.</p> Signup and view all the answers

    What role does DNA Polymerase play in DNA replication?

    <p>It synthesizes DNA from deoxyribonucleotides.</p> Signup and view all the answers

    How is the negative charge of the DNA backbone neutralized?

    <p>By the binding of positively charged proteins.</p> Signup and view all the answers

    What characterizes the major groove of the DNA double helix?

    <p>It is the primary site for protein binding.</p> Signup and view all the answers

    What role do TRF1 and TRF2 play in telomere structure?

    <p>They stabilize telomeres and protect chromosome ends.</p> Signup and view all the answers

    Which of the following accurately describes a difference between prokaryotic and eukaryotic RNA synthesis?

    <p>Prokaryotic ribosomes can begin translation before transcription finishes.</p> Signup and view all the answers

    What characteristic distinguishes RNA from DNA at the molecular level?

    <p>RNA has a ribose sugar instead of deoxyribose.</p> Signup and view all the answers

    Which type of RNA is primarily involved in the splicing and processing of RNA?

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

    What is the primary consequence of defective telomere maintenance in Werner Syndrome?

    <p>Premature aging and genomic instability.</p> Signup and view all the answers

    Which component is essential for the structure and function of prokaryotic ribosomes?

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

    Which of the following statements about telomerase activity in cancer cells is true?

    <p>Increased telomerase activity allows cancer cells to divide indefinitely.</p> Signup and view all the answers

    Which type of RNA is primarily involved in regulating the stability and translation of mRNA?

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

    What is the function of telomere binding proteins like TRF1 and TRF2?

    <p>To protect chromosome ends and prevent DNA breaks.</p> Signup and view all the answers

    What essential role does ribosomal RNA (rRNA) play during embryogenesis?

    <p>Providing high levels for protein synthesis.</p> Signup and view all the answers

    What is the role of the Shine-Dalgarno sequence during the initiation of translation in prokaryotes?

    <p>It pairs with the 16S rRNA to position the first AUG codon in the P site.</p> Signup and view all the answers

    Which of the following factors is involved in blocking the A site during translation initiation in eukaryotes?

    <p>eIF1A</p> Signup and view all the answers

    What is the primary function of EF-G during the elongation stage of translation?

    <p>It translocates the ribosome along the mRNA.</p> Signup and view all the answers

    Which initiation factor is responsible for preventing the premature association of the large ribosomal subunit in prokaryotes?

    <p>IF3</p> Signup and view all the answers

    What is the function of the eIF4 complex during the initiation of translation in eukaryotes?

    <p>It unwinds mRNA, binds the 5’ cap, and circularizes mRNA.</p> Signup and view all the answers

    During termination, what triggers the release of the polypeptide from the ribosome?

    <p>The entry of a water molecule.</p> Signup and view all the answers

    Which of the following statements accurately describes the elongation phase of translation?

    <p>Peptide bond formation occurs between the tRNAs at the A and P sites.</p> Signup and view all the answers

    Which of the following correctly describes the roles of RF1 and RF2 during termination in eukaryotes?

    <p>They recognize stop codons and stimulate peptide release.</p> Signup and view all the answers

    Study Notes

    DNA Structure and Replication

    • DNA carries necessary information for an organism's formation.
    • It's transmitted from parent to offspring.
    • DNA replicates itself for inheritance.
    • Variation explains phenotypic diversity.
    • Central dogma: DNA → RNA → Protein.
    • Transcription: DNA → RNA.
    • Translation: RNA → Protein.
    • Epigenetics: DNA modification and inheritance.
    • RNA types not leading to proteins: miRNA, siRNA, IncRNA, piRNA.

    Key Experiments

    • Griffith (1928): Transformation in Bacteria. -Type S (smooth): lethal, protective capsule. -Type R (rough): non-lethal, no capsule. -R strain became virulent (S) when mixed with heat-killed S strain. -Transformation: Something from dead S cells transformed R cells.

    • Avery, MacLeod, and McCarty (1944): DNA as transforming agent. -Only destroying DNA in type S cells prevented live S strain recovery.

    • Hershey and Chase (1952): DNA enters E. coli, confirming DNA as the genetic material. -Studied bacteriophage T2 virus (only DNA and protein). -Isotope labeling: 32P labels DNA, 35S labels protein. -Used radioactive phages to infect E. coli.

    DNA Structure

    • Watson and Crick (1953): Created the first correct DNA model using Rosalind Franklin's X-ray diffraction data.
    • Double helix: Two strands coiled around each other.
    • Nucleotides: building blocks of DNA.
    • Components of Nucleotides: Phosphate group, deoxyribose sugar, nitrogenous base (A, T, C, G).
    • Phosphomonoester bond: Ribose sugar to phosphate.

    DNA Replication

    • Semiconservative Replication (Meselson & Stahl, 1958): Each parent strand serves as a template for a new strand.
    • DNA polymerase III: Synthesizes new DNA in 5' to 3' direction.
    • Primase: Adds RNA primers to initiate DNA synthesis.
    • Ligase: Joins Okazaki fragments on the lagging strand.
    • Helicase: Unwinds DNA.
    • DNA polymerase I: Removes primers, and replaces with DNA, has proofreading (3' to 5' exonuclease) function.
    • Single-strand binding protein: prevents rejoining of strands.

    Central Dogma

    • Transcription (DNA → RNA): -RNA polymerase enzymes synthesizes RNA using DNA as a template. -The synthesized RNA product is messenger RNA (mRNA).
    • Translation (RNA → Protein): - Ribosomes read messenger RNAs (mRNA) to create proteins. - Specific transfer RNA (tRNA) molecules carry specific amino acids to the ribosome. -Amino acids are linked together to form polypeptides (proteins).

    Replication-Speed and Accuracy

    • Speed: DNA polymerase III in E. coli synthesizes 2,000 nucleotides per second.
    • Accuracy: 1 error per 10^10 nucleotides.
    • Proofreading: DNA polymerase III has 3' to 5' exonuclease activity to correct errors.

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    Genetics Final Exam PDF

    Description

    Test your knowledge on the fundamental aspects of DNA structure and replication. This quiz covers essential topics such as the central dogma of molecular biology, key experiments that established DNA as the genetic material, and the processes of transcription and translation. Explore the fascinating world of genetics and inheritance!

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