Introduction to Macromolecules
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Questions and Answers

What is the process by which a DNA double helix makes an identical copy of itself?

  • Transcription
  • Replication (correct)
  • Translation
  • Mutagenesis

    • What is the function of histones in eukaryotic DNA?

  • To serve as a template for DNA replication
  • To catalyze enzymatic reactions
  • To condense and organize DNA into nucleosomes (correct)
  • To provide a motor function for DNA movement

    • What is the polarity of DNA?

  • 5’-phosphate end and a 3’-hydroxyl end (correct)
  • 5’-hydroxyl end and a 3’-phosphate end
  • Both strands are identical
  • No polarity

    • What is the function of topoisomerase in DNA replication?

    <p>To relieve overwound supercoils</p> Signup and view all the answers

    What is the direction of DNA synthesis in eukaryotes?

    <p>5’-&gt;3’ direction</p> Signup and view all the answers

    What is the function of DNA ligase in DNA replication?

    <p>To seal nicks</p> Signup and view all the answers

    What is the mode of DNA replication in eukaryotes?

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

    What is the function of flap endonuclease 1 in DNA replication?

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

    What is the function of RNA primer in DNA synthesis?

    <p>To supply a free 3'-OH group for DNA synthesis</p> Signup and view all the answers

    What is the role of the sigma factor in prokaryotic transcription?

    <p>To increase the specificity for promoter and initiation</p> Signup and view all the answers

    What type of breaks does Topoisomerase II create?

    <p>Double-strand breaks</p> Signup and view all the answers

    What is the function of Telomerase?

    <p>To extend telomere sequences</p> Signup and view all the answers

    What is the function of the phosphonylation of the CTD tail on RNA pol II?

    <p>To regulate the rate-limiting step in RNA synthesis</p> Signup and view all the answers

    What is the first step in DNA repair mechanisms?

    <p>Recognizing a distortion in the DNA helix</p> Signup and view all the answers

    What is the primary function of snRNPs in RNA processing?

    <p>To remove introns from pre-mRNA</p> Signup and view all the answers

    What type of mutation would result in a premature stop codon?

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

    What type of repair is responsible for correcting base pair mismatches?

    <p>Mismatch Repair</p> Signup and view all the answers

    What is the function of CRISPR?

    <p>To mutate, activate, or deactivate parts of the genome</p> Signup and view all the answers

    What is the function of the A-site on the ribosome?

    <p>To accept the incoming aminoacyl-tRNA</p> Signup and view all the answers

    What is the energy source for the elongation step of protein synthesis?

    <p>GTP hydrolysis</p> Signup and view all the answers

    What is unique about the 2'-OH group on ribose in RNA?

    <p>It can chelate metal ions</p> Signup and view all the answers

    What type of RNA is synthesized by RNA polymerase II?

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

    What is the function of chaperone proteins?

    <p>To facilitate protein folding</p> Signup and view all the answers

    What is the function of FEN1/DNA polymerase I?

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

    What is the function of the TATA box?

    <p>To initiate RNA synthesis</p> Signup and view all the answers

    What is the mechanism of action of Rifampicin?

    <p>It inhibits RNA synthesis by binding to RNA polymerase</p> Signup and view all the answers

    What type of RNA is involved in the recognition and decoding of the genetic code?

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

    What is the function of the termination factors (RF-1, RF-2, RF-3) in protein synthesis?

    <p>To terminate protein synthesis</p> Signup and view all the answers

    Study Notes

    Central Dogma

    • Describes the flow of genetic information: DNA replication, transcription into mRNA, and translation into proteins.

    Replication

    • DNA double helix creates an identical copy using parent strands as templates.
    • Key enzymes:
      • Helicase unwinds DNA helix using ATP.
      • Topoisomerase relieves supercoiling.
      • Single-stranded binding proteins stabilize separated strands.
    • Semiconservative mechanism: each parental strand serves as a template for new strands.

    Transcription

    • Genetic information in DNA converted to mRNA.
    • Eukaryotic transcription requires RNA polymerase II and a TATA box for initiation.

    Translation

    • mRNA translates to proteins via ribosomes.
    • Codons (three-nucleotide sequences) specify amino acids during the process.

    Exceptions to the Central Dogma

    • RNA viruses use RNA as genetic material (e.g., Influenza uses viral RNA polymerase).
    • HIV utilizes reverse transcriptase for DNA synthesis.
    • Prions are proteins causing diseases by inducing misfolding in normal proteins.

    Eukaryotic DNA Structure

    • DNA localized in the nucleus, coiled around positively charged histones.
    • Nucleosomes formed by histone protein octamers.
    • Histone modifications (e.g., acetylation) regulate gene access.

    DNA Biochemistry

    • Antiparallel, linear double helix structure stabilized by hydrogen bonds.
    • Negatively charged DNA denatured under alkaline conditions.

    Gel Electrophoresis

    • Technique for separating and visualizing DNA fragments, utilizing DNA's properties.

    Topoisomerases

    • Topo I causes single-strand breaks to relieve tension.
    • Topo II creates double-strand breaks and requires ATP, targeted by specific antibiotics.

    RNA Primer Requirement

    • An RNA primer synthesized by primase is necessary for DNA synthesis, providing a free 3’-OH group.

    Telomerase

    • Extends telomeres (repeating sequences at chromosome ends) using its RNA template to prevent senescence.

    DNA Damage and Repair Mechanisms

    • DNA damage involves structural alterations, with repair processes including:
      • Nucleotide Excision Repair: fixes distortions by excising damaged segments.
      • Base Excision Repair: addresses mismatches or small damages; involves DNA glycosylase.
      • Mismatch Repair: corrects nucleotide errors in newly synthesized DNA.
    • Genetic deficiencies in repair mechanisms can lead to diseases such as Xeroderma Pigmentosum and Lynch Syndrome.

    CRISPR

    • A technology utilizing DNA repair mechanisms for genome editing.

    RNA vs. DNA

    • RNA contains 2’-OH on ribose, allowing interactions with metal ions, and is usually single-stranded.

    Types of RNA

    • RNA polymerase I synthesizes rRNA, II synthesizes mRNA, and III synthesizes tRNA.

    Inhibition of RNA Polymerases

    • Rifampicin inhibits bacterial RNA polymerase; α-amanitin blocks eukaryotic RNA polymerase II.

    Transcription in Prokaryotes

    • Initiated by RNA polymerase with a sigma factor for promoter specificity.

    Eukaryotic Transcription

    • Involves transcription factors and phosphorylation of RNA pol II’s CTD tail, necessary for initiation.

    RNA Processing

    • Pre-mRNA undergoes modifications like capping, polyadenylation, and splicing to produce mature mRNA.

    Splicing

    • Introns (non-coding regions) are removed, requiring snRNPs, which are essential for the splicing mechanism.

    Genetic Mutation Types

    • Various mutations include:
      • Point: single nucleotide change.
      • Silent: same amino acid specified.
      • Missense: different amino acid specified.
      • Nonsense: produces a stop codon.
      • Insertion: addition of bases.
      • Deletion: loss of bases.

    Ribosome Structure

    • Composed of 65% rRNA and 35% protein, crucial for peptide bond formation during translation.

    tRNA Function

    • Contains anticodons that pair with mRNA to ensure proper amino acid sequence.

    Amino Acid Activation

    • Requires ATP for the "charging" process by aminoacyl-tRNA synthetases.

    Protein Synthesis Elongation

    • Employs energy from GTP hydrolysis and involves multiple steps including peptide bond formation.

    Termination of Protein Synthesis

    • Triggered by stop codons, leading to the release of the peptide and ribosomal subunit dissociation.

    Chaperone Proteins and Modifications

    • Facilitate proper protein folding and modifications such as cleavage and functional group additions for final protein functionality.

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    Quiz Team

    Description

    Understand the process of replication, transcription, and translation in the central dogma, and explore exceptions to this rule, including RNA viruses.

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