chapter 1 and 2 MBG
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Questions and Answers

What catalyzes the separation of DNA strands?

  • High temperature
  • Chemical reaction
  • Mechanical force
  • Different enzymic activities (correct)

    • DNA can only be denatured at the start or end regions.

    False

    What is hybridization in nucleic acids?

    Creating a hybrid from two different DNA or RNA strands.

    The double helix will form again during hybridization if the temperature is progressively __________.

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

    Match the following terms with their definitions:

    <p>Denaturation = Separation of DNA strands Hybridization = Formation of a new hybrid from different strands Replication = Copying of DNA Transcription = Synthesis of RNA from DNA</p> Signup and view all the answers

    What is the primary purpose of controlling gene expression?

    <p>To conserve energy and resources</p> Signup and view all the answers

    Operons are only found in eukaryotic cells.

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

    What are the components of transcriptional control processes?

    <p>Initiation, elongation, termination</p> Signup and view all the answers

    A small piece of DNA upstream the gene that contains information on how to control said gene is called a __________.

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

    Match the following processes with their respective stages of transcription:

    <p>Initiation = The start of transcription Elongation = Addition of nucleotides to the growing RNA strand Termination = Ending the transcription process Processing = Modifying the newly formed RNA</p> Signup and view all the answers

    What role do Sigma factors play in bacteria?

    <p>They regulate gene expression.</p> Signup and view all the answers

    Sigma factors are only required for normal growth in bacteria regardless of environmental conditions.

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

    What is the sequence recognized by promoters on -10 in E. coli?

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

    Some Sigma factors are essential for __________ events like nitrogen regulation.

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

    Match the following Sigma factors with their specific functions:

    <p>Sigma 54 = Nitrogen regulation Sigma 32 = Response to heat shock Sigma 70 = General transcription for cell growth Sigma 38 = Starvation response</p> Signup and view all the answers

    What is the melting point (TM) of DNA defined as?

    <p>The temperature at which 50% of the DNA is single-stranded</p> Signup and view all the answers

    Higher percentages of Guanine and Cytosine (G and C) in DNA result in a lower melting point.

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

    What formula is used to determine the melting point (TM) based on the composition of DNA?

    <p>IM = 4x(GC) + 2x(AT)</p> Signup and view all the answers

    DNA denaturation occurs when temperature is increased, leading to the ______ of the double strands.

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

    What happens to DNA when it is denatured?

    <p>It absorbs more light</p> Signup and view all the answers

    The reassociation of DNA occurs at temperatures above the melting point.

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

    What effect does the melting point have on the average GC content of a given DNA molecule?

    <p>The average GC content can be determined from the melting point.</p> Signup and view all the answers

    What is the primary function of mRNA?

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

    Polycistronic RNA is transcribed from multiple operons.

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

    What are the three main types of RNA?

    <p>mRNA, rRNA, tRNA</p> Signup and view all the answers

    During transcription, RNA polymerase adds nucleosides on the ___ direction.

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

    Match each type of RNA with its primary function:

    <p>mRNA = Encodes protein rRNA = Forms the core of ribosomes tRNA = Brings amino acids to mRNA RNA polymerase = Enzyme that synthesizes RNA</p> Signup and view all the answers

    What is the role of tRNA in translation?

    <p>To bring amino acids to the mRNA</p> Signup and view all the answers

    Transcription and translation can occur simultaneously in prokaryotic cells.

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

    What does the open complex refer to in the transcription process?

    <p>Separation of DNA strands where RNA polymerase reads the template strand.</p> Signup and view all the answers

    Which phase of metabolism indicates that bacteria are rapidly dividing?

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

    All genes are regulated by constitutive promoters.

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

    What are the two types of transcription termination?

    <p>Rho independent and Rho dependent</p> Signup and view all the answers

    Rho dependent termination involves a hexameric protein with ______ activity that helps terminate transcription.

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

    What kind of genes can be controlled like a light switch?

    <p>Inducible genes</p> Signup and view all the answers

    Match the following transcription factor functions with their descriptions:

    <p>Sigma factor = Binds to -35 region of DNA Anti-sigma factor = Inhibits transcription factors Housekeeping genes = Frequently expressed genes Inducible genes = Expression regulated by external signals</p> Signup and view all the answers

    Rho independent termination requires the Rho protein.

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

    What is the purpose of the attenuator site in transcription?

    <p>To determine whether RNAP continues or terminates transcription</p> Signup and view all the answers

    During Rho dependent termination, Rho binds to the ______ sequence on the RNA.

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

    Which of the following best describes housekeeping genes?

    <p>Required for basic cellular functions</p> Signup and view all the answers

    Inducible genes are always expressed at a constant level.

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

    What role does the stem loop structure play in transcription termination?

    <p>It causes RNAP to stop transcription.</p> Signup and view all the answers

    Rho independent termination has two features: GC rich regions and a series of ______ residues.

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

    What happens when tryptophan is present in terms of transcription?

    <p>Transcription is blocked</p> Signup and view all the answers

    Match the following RNA structures with their roles:

    <p>Stem Loop = Causative factor for RNAP termination SI Sequence = Rho binding site Promoter = Site of transcription initiation Attenuator = Controls transcription continuation or termination</p> Signup and view all the answers

    Study Notes

    Molecular Biology

    • Molecular biology is the study of gene structure and function at the molecular level.
    • A gene is composed of cellular chemicals.
    • Genes control cellular function.
    • Physics explains the thermodynamics of genes.
    • Nucleic acids are made of nitrogenous bases, purines, and pyrimidines.
    • Purines include adenine and guanine.
    • Pyrimidines include cytosine, thymine, and uracil.
    • Phosphoric acid (H3PO4) is a component of nucleic acids.
    • Pentose sugars (ribose and deoxyribose) are also components of nucleic acids.
    • Nucleosides are formed by glycoside bonds between nitrogenous bases and pentose sugars.
    • Phosphodiester bonds form between nucleotides.
    • DNA is acidic due to phosphate groups.
    • DNA is double stranded.
    • DNA has complementary and anti-parallel strands; the strands are twisted around each other in a helix.
    • Hydrogen bonds hold complementary DNA strands together.
    • DNA exists in different forms (A, B, Z).
    • DNA absorbs ultraviolet (UV) light at a wavelength of 200 nm.
    • Single-stranded DNA (ssDNA) absorbs more UV light than double-stranded DNA (dsDNA).
    • DNA's melting temperature (Tm) depends on the G-C content of the DNA. A higher G-C content results in a higher melting temperature.

    Nucleic Acid Hybridization

    • Nucleic acid hybridization is the process of creating a new hybrid from two different DNA or RNA strands.
    • Hybridization occurs when complementary strands of DNA or RNA bond together.
    • Hybridization can occur in solution or on solid supports like bacteria colonies, chromosomes, and tissue sections.
    • DNA can be denatured, typically at elevated temperatures.
    • Denatured DNA can re-form a double helix when cooled.
    • This re-formation is called hybridization.

    Transcription in Prokaryotes

    • Transcription is the process of creating RNA from DNA.
    • Bacteria are efficient in controlling transcription and translation.
    • Genes are turned on and off in response to environmental changes.
    • Bacteria conserve energy by only transcribing genes when needed.
    • Transcriptional control involves initiation, elongation, and termination.
    • Operons are groups of genes that are transcribed together.
    • Transcription in prokaryotes usually involves polycistronic RNA.
    • Multiple genes are transcribed as a single transcript and translation occurs simultaneously.
    • Types of RNA: Messenger RNA (mRNA), Ribosomal RNA (rRNA), and Transfer RNA (tRNA).
    • RNA polymerase is needed for RNA synthesis.

    Prokaryotic Transcription Initiation

    • RNA polymerase (RNAP) is used to synthesize mRNA.
    • Prokaryotic RNAP is composed of subunits (alpha, beta, beta') with a sigma factor.
    • The sigma factor recognizes and binds to promoter regions, which are essential for initiating transcription.
    • Promoters have two major elements, the -35 region and the -10 region.
    • Promoters are located upstream of the initiation site (+1).
    • Transcription starts at position +1.
    • Sigma factors regulate which regions/genes are transcribed in response to a variety of cellular signals.
    • Sigma factors have distinct domains for binding to different regulatory elements in promoters.

    Transcriptional Control Processes

    • Constitutive promoters do not have regulatory elements.
    • Inducible promoters do have regulatory elements.
    • Transcriptional attenuation is a control mechanism used in bacteria.
    • Transcriptional attenuation involves the formation of specific secondary structures in the mRNA.

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    Introduction to Molecular Biology PDF

    Description

    Dive into the fascinating world of molecular biology, where we explore gene structure and function at the molecular level. Understand the components of nucleic acids, the role of purines and pyrimidines, and the intricate details of DNA's structure. This quiz will test your knowledge of fundamental concepts in molecular biology.

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