Molecular Biology: PCR and Lac Operon Quiz
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Questions and Answers

What is the main purpose of the Polymerase Chain Reaction (PCR)?

  • To digest proteins
  • To sequence DNA
  • To amplify a specific DNA region (correct)
  • To transform cells

    • During the denaturation step of PCR, DNA strands are cooled to separate them.

    False

    What is the role of DNA Polymerase in PCR?

    To synthesize new DNA strands using nucleotides.

    In PCR, the temperature for annealing must be __________ degrees below the melting temperature.

    <p>5</p> Signup and view all the answers

    Match the components of PCR to their functions:

    <p>Primers = Initiate DNA synthesis DNA Nucleotides = Building blocks for new DNA DNA Polymerase = Adds nucleotides to the new strand Buffer = Maintains pH and ionic balance during PCR</p> Signup and view all the answers

    How are DNA strands separated in the denaturation step of PCR?

    <p>By heating the mixture</p> Signup and view all the answers

    For every cycle of PCR, the number of DNA molecules produced doubles.

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

    Gel electrophoresis is used to separate charged macromolecules based on their __________.

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

    Which component is NOT typically found in a tryptophan operon?

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

    Tryptophan acts as a competitive inhibitor during feedback inhibition.

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

    What is the function of LacZ in the lac operon?

    <p>It codes for an enzyme that turns lactose into simple sugars.</p> Signup and view all the answers

    In the absence of glucose, elevated levels of __________ will lead to the activation of the CAP site.

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

    Match the components of the lac operon with their functions:

    <p>LacZ = Codes for enzyme breaking down lactose LacY = Allows absorption of lactose LacA = Helper gene LacI = Repressor of the operon</p> Signup and view all the answers

    Which situation leads to transcription in the lac operon?

    <p>No glucose and high lactose</p> Signup and view all the answers

    The lac repressor is activated when there is high lactose present.

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

    What binds to the shine-dalgarno sequence to initiate protein synthesis in prokaryotes?

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

    Which component is needed to express eukaryotic genes in prokaryotic cells?

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

    A negative control in an experiment should contain the target protein.

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

    What is the purpose of using a positive control in experiments such as northern blotting?

    <p>To provide a reference point for what a positive result should look like.</p> Signup and view all the answers

    Bacteria use ________ sensing to communicate about external conditions.

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

    Match the following terms with their descriptions:

    <p>Western Blotting = Technique to detect specific proteins using antibodies SDS-PAGE = Method for separating proteins based on size cDNA = Complementary DNA used for cloning and expression Loading Control = Marker to ensure equal protein loading in wells</p> Signup and view all the answers

    Which of the following is a common loading control used in protein assays?

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

    Yeast Saccharomyces Cerevisiae has four mating types.

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

    What is the role of beta-mercaptoethanol in the gel electrophoresis process?

    <p>It provides reducing conditions to break disulfide bonds in proteins.</p> Signup and view all the answers

    What is the role of second messengers like cAMP in cell signaling?

    <p>They amplify cell signals.</p> Signup and view all the answers

    Homologous chromosomes consist of sister chromatids.

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

    What term describes the abnormal number of chromosomes in a cell?

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

    During interphase, the cell primarily engages in normal cellular functions and may enter the ______ phase if it ceases to divide.

    <p>G0</p> Signup and view all the answers

    What process utilizes the Ras-RAF-MEK-ERK pathway in cancer cells?

    <p>Cell signaling</p> Signup and view all the answers

    Sister chromatids are held together by a centromere.

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

    What phase of the cell cycle is primarily responsible for cell growth?

    <p>G1 Phase</p> Signup and view all the answers

    Which of the following best describes endocrine signaling?

    <p>Signaling that releases ligands into the bloodstream for long-distance communication.</p> Signup and view all the answers

    Steroids activate transcription in the cytoplasm.

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

    What type of receptors must bind two ligands to form a dimer in order to activate?

    <p>Receptor tyrosine kinases (RTK)</p> Signup and view all the answers

    _____ signaling occurs when a cell sends out a ligand that activates its own cell membrane.

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

    Match the types of membrane receptors with their descriptions:

    <p>Receptor Tyrosine Kinases (RTK) = Require two ligands to form a dimer for activation G Protein Coupled Receptors = Activate signaling by exchanging GDP for GTP Ligand Gated Ion Channels = Open to allow ions in when activated by a ligand</p> Signup and view all the answers

    What is the role of the G protein in G Protein Coupled Receptors?

    <p>To release GDP and bind GTP to send the signal out.</p> Signup and view all the answers

    Gap junctions are a method of long-distance communication in multicellular organisms.

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

    What transformation occurs to GTP during the deactivation of G proteins?

    <p>GTP turns into GDP</p> Signup and view all the answers

    What is the primary function of the S Phase in the cell cycle?

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

    Nondisjunction during mitosis results in both daughter cells being properly formed.

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

    List the four main stages of mitosis in order.

    <p>Prophase, Metaphase, Anaphase, Telophase</p> Signup and view all the answers

    The structure that is responsible for pulling sister chromatids apart during mitosis is the ______.

    <p>spindle fibers</p> Signup and view all the answers

    Match the following phases of the cell cycle with their primary activities:

    <p>G2 = Preparation for mitosis M Phase = Mitosis occurs Cytokinesis = Division of cytoplasm S Phase = DNA replication</p> Signup and view all the answers

    Which factor allows normal cells to stop dividing once a certain density is reached?

    <p>Density Dependent Inhibition</p> Signup and view all the answers

    Cancer cells require attachment to a surface to grow and proliferate.

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

    What happens during Telophase?

    <p>The nuclear membrane reappears and chromosomes decondense into chromatin.</p> Signup and view all the answers

    Study Notes

    PCR (Polymerase Chain Reaction)

    • PCR is the amplification of a specific DNA region, not requiring a cell.
    • Needs: A target DNA sequence, primers, DNA polymerase, nucleotides.
    • Steps:
      • Denaturation (94-98°C): Separate DNA strands.
      • Annealing (50-68°C): Primers attach to target sequence.
      • Elongation (72°C): DNA polymerase extends primers using nucleotides.
    • This process repeats to exponentially increase copies.

    Gel Electrophoresis

    • Separates charged macromolecules (e.g., DNA) based on size.
    • Uses a gel matrix (agarose or polyacrylamide).
    • DNA migrates towards the positive pole.
    • Larger fragments move slower, remaining closer to the top of the gel.
    • DNA visualization: Stain the gel and view it under UV light.

    Sanger Sequencing

    • Identifies the order and type of nucleotides in a DNA segment.
    • Uses dideoxynucleotides (ddNTPs): These terminate DNA synthesis at specific points.
    • Different ddNTPs are fluorescently labeled, enabling sequence determination.
    • Procedure involves multiple reactions, separated fragments, and then reading an X-ray.

    Modern Sanger Sequencing Advantages

    • Fluorescent labeling of ddNTPs allows for the use of single tubes instead of four.
    • Capillary electrophoresis with CCD detection enhances efficiency.

    Central Dogma

    • The flow of genetic information from DNA to RNA to protein.
    • DNA stores genetic instructions for protein synthesis.
    • mRNA carries these instructions to ribosomes for protein production.

    Prokaryotic Transcription/Translation

    • DNA is transcribed to mRNA, translating to protein.
    • No separation of transcription and translation.
    • Operons are a group of genes that are transcribed together.
    • Tryptophan operon: Encoded for a series of enzymes to synthesize tryptophan.
    • The amount of tryptophan influences transcription activity.
    • High levels of tryptophan can reduce enzyme levels, acting as a corepressor.
    • Lac operon: Involved in lactose metabolism.
    • High glucose levels and the lack of lactose will inhibit transcription of lac operons.

    Eukaryotic Transcription/Translation

    • mRNA, rRNA, and tRNA synthesis occur in the nucleus.
    • Translation occurs in the cytoplasm.
    • mRNA undergoes processing (splicing, 5' cap, 3' poly-A tail).
    • Transcription and translation are separated in time and space.
    • RNA polymerase I, II, and III create different kinds of RNA (rRNA, mRNA, and tRNA).

    Effects of Mutations

    • Substitutions: Silent mutation- Codes for the same amino acid. Mis-sense mutation- Codes for a different amino acid. Nonsense- Codes for a premature stop codon.
    • Insertions/Deletions: Frameshift mutations change the reading frame, often leading to nonfunctional proteins.

    Gene Expression Detection

    • Northern blotting detects RNA.
    • Western blotting detects proteins.
    • RT-PCR is used for cDNA synthesis and amplification from RNA.
    • Fluorescent in situ hybridization (FISH): Visualizes mRNA or DNA locations in cells.

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    Description

    Test your knowledge on the Polymerase Chain Reaction (PCR) and the lac operon. This quiz covers key concepts such as the role of DNA polymerase, the denaturation step in PCR, and the function of components in the lac operon. Perfect for students looking to solidify their understanding of molecular biology methods and mechanisms.

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