Central Dogma and DNA Replication Quiz
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Questions and Answers

What is the first step in the Central Dogma of Molecular Biology?

  • DNA replication
  • Transcription (correct)
  • Translation
  • Post-translational modification

    • Which of the following molecules is produced during transcription?

  • mRNA (correct)
  • tRNA
  • rRNA
  • DNA

    • During which process is the genetic information from mRNA translated into a protein?

  • DNA modification
  • Translation (correct)
  • Transcription
  • Replication

    • What is the result of DNA replication?

    <p>Two identical DNA molecules</p> Signup and view all the answers

    Which of the following describes the process of translating mRNA into protein?

    <p>Using ribosomes and transfer RNA</p> Signup and view all the answers

    What is the correct order of the processes in the Central Dogma?

    <p>Transcription, Replication, Translation</p> Signup and view all the answers

    What role do enzymes play in DNA replication?

    <p>They assist in achieving high fidelity during replication.</p> Signup and view all the answers

    What is the complementary role of messenger RNA in the Central Dogma?

    <p>Conveying genetic information from DNA to ribosomes</p> Signup and view all the answers

    What is the role of the sliding clamp during DNA replication?

    <p>It stabilizes the DNA polymerase on the DNA.</p> Signup and view all the answers

    Which strand is synthesized continuously during DNA replication?

    <p>Leading strand</p> Signup and view all the answers

    What are the short segments formed on the lagging strand called?

    <p>Okazaki fragments</p> Signup and view all the answers

    Which enzyme is responsible for removing RNA primers during DNA replication?

    <p>RNAse H</p> Signup and view all the answers

    How does DNA polymerase contribute to the lagging strand synthesis?

    <p>It fills in the gaps after the RNA primers are removed.</p> Signup and view all the answers

    What is the end result of joining Okazaki fragments together?

    <p>Creation of a continuous DNA strand</p> Signup and view all the answers

    Which of the following statements is true regarding RNAse H?

    <p>It degrades RNA by hydrolyzing its phosphodiester bonds.</p> Signup and view all the answers

    What purpose does ligase serve in DNA replication?

    <p>It joins Okazaki fragments.</p> Signup and view all the answers

    What is the primary function of RNase H in DNA replication?

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

    Which of the following accurately describes the leading strand in DNA replication?

    <p>Synthesized continuously</p> Signup and view all the answers

    Why can DNA polymerase only synthesize DNA in the 5’ to 3’ direction?

    <p>It is structurally unable to add nucleotides in the opposite direction</p> Signup and view all the answers

    What is the role of DNA ligase during DNA replication?

    <p>To join DNA fragments by forming bonds</p> Signup and view all the answers

    What is true regarding the discontinuous strand during DNA replication?

    <p>It is made in fragments known as Okazaki fragments</p> Signup and view all the answers

    How do the two parental DNA strands move through the replication factory?

    <p>In the same direction, allowing continuous synthesis</p> Signup and view all the answers

    What is formed when DNA polymerase synthesizes the daughter strands?

    <p>One leading strand and one lagging strand</p> Signup and view all the answers

    Which statement about the template strands during DNA replication is true?

    <p>Synthesis occurs only at the 3’ end of each strand</p> Signup and view all the answers

    Which element is specifically associated with eukaryotic promoters to facilitate the access of RNA Pol II?

    <p>TATA box</p> Signup and view all the answers

    What type of enzyme is RNA Pol II described as?

    <p>A multiunit regulated enzyme</p> Signup and view all the answers

    What is the role of upstream activation sequences in eukaryotic genes?

    <p>To enhance access to promoters</p> Signup and view all the answers

    Which of the following is NOT a characteristic of eukaryotic promoters compared to prokaryotic promoters?

    <p>Single unit regulatory factor</p> Signup and view all the answers

    Which functional role do responsive elements have in relation to RNA Pol II?

    <p>They mediate interaction with RNA Pol II</p> Signup and view all the answers

    What is a feature of the initiation sequences in transcription for eukaryotes?

    <p>They include transcription elements.</p> Signup and view all the answers

    How do prokaryotic and eukaryotic promoters differ fundamentally?

    <p>Prokaryotic promoters do not require regulatory proteins.</p> Signup and view all the answers

    What aspect of transcription does the chromatin structure primarily influence in eukaryotes?

    <p>Access of regulatory proteins to promoters</p> Signup and view all the answers

    What is the function of the TATA-binding protein (TBP) at the initiation site?

    <p>It unwinds the DNA helix and assembles transcription factors.</p> Signup and view all the answers

    Which transcription factors bind after the TATA-binding protein during the initiation of transcription?

    <p>TFIIB and TFIIA</p> Signup and view all the answers

    What is the role of the RNA polymerase II in the transcription process?

    <p>It elongates the RNA transcript by adding nucleotides.</p> Signup and view all the answers

    What occurs in the 'pre-initiation complex' during transcription?

    <p>Various transcription factors bind to RNA polymerase II and DNA promoters.</p> Signup and view all the answers

    What happens to transcription if the TATA box is missing?

    <p>Transcription cannot initiate properly.</p> Signup and view all the answers

    How does DNA looping contribute to transcription?

    <p>It allows specific transcription factors at a distance to interact with the initiation complex.</p> Signup and view all the answers

    Which of the following is part of the transcription factors required for the initiation of transcription?

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

    What is one function of transcription factors in eukaryotic transcription?

    <p>They help direct RNA polymerase II to the promoter region.</p> Signup and view all the answers

    What is the primary role of eukaryotic initiation factors (eIFs) during the translation initiation process?

    <p>To recognize and bind to the initiator tRNA</p> Signup and view all the answers

    In prokaryotes, where does the initiation complex form during translation?

    <p>At the Shine-Dalgarno sequence just 5' to the coding region</p> Signup and view all the answers

    Which subunits compose the eukaryotic ribosome?

    <p>80S, consisting of 60S and 40S</p> Signup and view all the answers

    What is the first codon recognized during the translation initiation in eukaryotes?

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

    What is the function of ATP during the initiation stage of translation?

    <p>To provide energy for ribosome assembly</p> Signup and view all the answers

    How many initiation factors are involved in the prokaryotic translation initiation process?

    <p>3</p> Signup and view all the answers

    During translation, which aspect is shared between eukaryotes and prokaryotes?

    <p>The formation of a complex with initiator tRNA</p> Signup and view all the answers

    Which amino acid is selected by the codon UGG during translation?

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

    Study Notes

    Central Dogma

    • The central dogma describes the flow of genetic information, from DNA to RNA to protein.
    • DNA is transcribed into RNA.
    • RNA is translated into protein.

    Learning Outcomes

    • Describe DNA replication, comparing leading and lagging strands.
    • Describe the process of transcription.
    • Describe the process of translation.
    • Gain an overview of post-translational modifications.

    DNA Replication

    • DNA replication produces two identical DNA molecules, ensuring the transmission of genetic information faithfully.
    • Replication occurs at origins of replication.
    • Prokaryotic DNA typically has one origin.
    • Eukaryotic DNA has multiple origins.
    • Replication occurs during the S phase of the cell cycle.
    • Replication is bidirectional - originating from multiple origins
    • Uses a variety of proteins including DNA polymerase, helicase, and single-strand binding proteins to unwind and copy DNA
    • DNA polymerase is a hand-shaped enzyme that copies DNA
    • Leading strand synthesized continuously.
    • Lagging strand synthesized in short fragments (Okazaki fragments)
    • Enzymes (RNase H & DNA ligase) work together to link Okazaki fragments
    • DNA polymerase moves along template strands in 3' → 5'.

    Cell Cycle (Mitosis)

    • Nucleic acids store and transmit genetic information.
    • Before cell division, DNA replicates with high fidelity.
    • The cell cycle progresses through G0, G1, S, G2, and M phases.

    Origin of Replication (ori)

    • Origin of replication (ori) is a specific region of the DNA sequence in the genome where DNA replication is first initiated.
    • Prokaryotes usually have one origin of replication.
    • Eukaryotes often have multiple origins for efficiency.
    • The origins of replication are activated in the S phase of the cell cycle.

    Transcription

    • Transcription is the process of making an RNA copy of a DNA sequence.
    • Prokaryotic transcription occurs in the cytosol
    • Eukaryotic transcription occurs within the nucleus.
    • Transcription is initiated at specific regions called promoters.
    • Requires RNA polymerase.
    • 3 stages: initiation, elongation, and termination.
    • Prokaryotes have one type of RNA polymerase.
    • Eukaryotes have 3 different RNA polymerases. RNA polymerase II primarily controls mRNA synthesis.

    Transcription in Prokaryotes

    • RNA polymerase binds to the promoter region.
    • RNA polymerase unwinds a section (transcription bubble) and synthesizes an RNA copy using NTPs.
    • RNA copy is synthesized 5' → 3' antiparallel and complementary to the template strand which is 3' → 5'
    • Termination is through Rho-dependent or Rho-independent mechanisms, which results in RNA termination and separation from the template DNA.

    Promoter

    • Promoter is the starting point of transcription.
    • Consensus sequences are recognized by RNA polymerase.
    • Includes -35 and -10 regions (prokaryotic)
    • TATA box is a consensus sequence for eukaryotic initiation.
    • Upstream elements/activation sequences also found on eukaryotic genes

    Elongation (prokaryotes)

    • RNA polymerase moves along the anti-sense strand.
    • NTPs complementary to the template are added.
    • Phosphodiester bonds form between the nucleotides.
    • DNA unwinds to expose the template strand for continuing elongation.
    • Topoisomerases are enzymes which relieve supercoiling stress during transcription

    Termination (prokaryotes)

    • Rho-independent termination: hairpin structure followed by a U-rich region. The hairpin causes RNA polymerase to pause.
    • Rho-dependent termination: Rho factor binds to RNA and moves towards RNA polymerase, causing it to release from the DNA

    Transcription in Eukaryotes

    • More complex than prokaryotic transcription.
    • Occur in the nucleus.
    • Multiple RNA polymerases (RNA polymerase II specifically for mRNA synthesis)
    • mRNA is synthesized in 5' → 3' direction.
    • Eukaryotic forms have TATA box, Inr, Upstream elements in the promoter regions.

    Initiation (eukaryotes)

    • TBP binds to the TATA box of the promoter, initiating the unwinding of the DNA.
    • Transcription factors (TFIIB and TFIIA) bind, along with RNA polymerase II.
    • Other factors bind to form a complete pre-initiation complex.

    Other Eukaryotic Transcription Factors

    • Activator proteins bind to enhancers which are sequences further away from the promoter regions
    • Coactivators interact with the pre-initiation complex to enhance transcription rate.
    • Repressors bind to proteins to suppress transcription rate

    mRNA produced in prokaryotes and eukaryotes

    • Prokaryotic mRNA is polycistronic (codes for multiple proteins).
    • Eukaryotic mRNA is monocistronic (codes for a single protein)
    • Eukaryotic mRNA undergoes extensive processing. (removal of introns, 5' cap, 3' polyA tail.)

    Post-transcriptional processing in eukaryotes

    • Capping (5' end).
    • Addition of a poly(A) tail (3' end).
    • Removal of introns (splicing) and joining of exons (splicing).
    • This processing produces the mature mRNA used for translation

    Translation

    • Ribosomes translate mRNA into polypeptide chains, directing amino acids in based on the order in the mRNA.
    • Uses mRNA, tRNA, and ribosomes.
    • Genetic code is degenerate, meaning one amino acid is coded by multiple codons. The wobble hypothesis describes flexibility with the third position of the codon.
    • mRNA is read 5′ to 3′ and protein synthesis occurs from amino to carboxyl
    • Three stages: Initiation, Elongation, Termination

    Translation (Initiation- Eukaryotes)

    • Small ribosomal subunit binds to the mRNA 5' cap.
    • Initiator tRNA (Met-tRNA) binds, along with various initiation factors.
    • Large ribosomal subunit joins the complex to form the complete ribosome.
    • Ribosome moves to the start codon (AUG).

    Translation (Initiation- Prokaryotes)

    • Small ribosomal subunit binds to Shine-Dalgarno sequence
    • Initiator tRNA (Met-tRNA) binds
    • Large subunit joins
    • Ribosome identifies start codon (AUG)

    Translation (Elongation)

    • Aminoacyl-tRNA synthetases are enzymes that attach amino acids to tRNAs.
    • Incoming aminoacyl-tRNA binds at the A site.
    • Peptide bond forms between the amino acids.
    • Ribosome moves down the mRNA.
    • Empty tRNA moves to E-site and is released.

    Translation (Termination)

    • Stop codon (UAA, UAG, or UGA) enters the A-site.
    • No tRNA matches the stop codon.
    • Release factors bind, causing the polypeptide chain to be released and the ribosome to dissociate.

    Post-translational modifications

    • Occur in eukaryotes.
    • Modifications include glycosylation, phosphorylation, and others.
    • These modifications play crucial roles in protein function and activity

    DNA Topoisomerases

    • Enzymes that relieve supercoiling stress in DNA during replication and transcription.
    • Essential in regulating the topological state of the genetic material.

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    IC15 Central Dogma - PDF

    Description

    Test your understanding of the central dogma and the processes of DNA replication, transcription, and translation. This quiz will challenge you to describe the flow of genetic information and the roles of different enzymes involved in DNA replication. Learn about the distinctions between prokaryotic and eukaryotic DNA replication.

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