DNA Replication and Transcription Overview
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DNA Replication and Transcription Overview

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Questions and Answers

What is the result of tRNA binding to the A site during translation?

  • The mRNA is degraded
  • A peptide bond is formed between amino acids (correct)
  • The ribosome splits from the mRNA
  • The polypeptide chain is released from the ribosome

    • Gene mutations can only have negative effects on an organism.

    False

    What initiates the termination phase of translation?

    A stop codon appearing in the A site

    A ______ mutation occurs when a base is inserted or deleted from a gene.

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

    Match the types of mutations with their examples:

    <p>Chromosomal Mutation = Down Syndrome Point Mutation = Sickle-cell Anemia Frameshift Mutation = Tay-Sachs Disease</p> Signup and view all the answers

    What is the primary role of RNA polymerase during transcription?

    <p>To bond with promoter regions</p> Signup and view all the answers

    During transcription in eukaryotes, enzymes are involved in splicing the mRNA after it is synthesized.

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

    What signals the start of protein synthesis?

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

    The process of transcription produces _____ from a DNA template.

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

    Match the following terms with their correct descriptions:

    <p>Promoter = Region where RNA polymerase binds Splicing = Removing non-coding sequences from mRNA Codon = Three nucleotide sequence on mRNA Polysome = Complex of mRNA and ribosomes</p> Signup and view all the answers

    Which of the following describes the direction of translation?

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

    All codons have corresponding tRNA anticodons.

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

    What is the function of GTP during the initiation of translation?

    <p>To assist in the formation of the initiation complex</p> Signup and view all the answers

    What is the process known as when DNA is replicated in a way that preserves one original strand in each new double helix?

    <p>Semi-conservative replication</p> Signup and view all the answers

    The enzyme Helicase is responsible for creating covalent bonds between nucleotides during DNA replication.

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

    What is the role of DNA Ligase during DNA replication?

    <p>To bond Okazaki fragments together.</p> Signup and view all the answers

    During transcription, the strand of DNA that is copied is called the ______ strand.

    <p>anti-sense</p> Signup and view all the answers

    Match the following enzymes with their functions in DNA replication:

    <p>Helicase = Unwinds the DNA helix DNA Polymerase III = Joins new nucleotides to form the new strand DNA Polymerase I = Replaces RNA primers with DNA nucleotides DNA Ligase = Bonds Okazaki fragments together</p> Signup and view all the answers

    What is the direction of synthesis for the leading strand during DNA replication?

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

    In prokaryotes, mRNA undergoes processing before it is translated into proteins.

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

    What is the flow of genetic information as described in the central dogma?

    <p>DNA → RNA → Protein</p> Signup and view all the answers

    Study Notes

    DNA Replication

    • DNA replicates during interphase, before mitosis.
    • Meselson and Stahl, in 1957, demonstrated semi-conservative replication using California Institute of Technology.
    • Experiment confirmed that replication follows a semi-conservative process.
    • Unwinding is performed by the enzyme helicase, which breaks hydrogen bonds between bases.
    • RNA primer binds to the old DNA strand.
    • DNA polymerase III adds new nucleotides to the exposed strand in a 5' to 3' direction.
    • Leading strand is continuous, lagging strand forms Okazaki fragments (discontinuous).
    • DNA polymerase I removes RNA primers and replaces them with DNA nucleotides.
    • DNA ligase joins Okazaki fragments.

    Transcription

    • DNA holds instructions for everything in the body but remains in the nucleus.
    • Nucleus protects DNA, it's only exposed during mitosis.
    • RNA is required to carry information from DNA to the rest of the cell.
    • Strand transcribed is the anti-sense strand; the unused strand is the sense strand.
    • mRNA is complementary to the anti-sense strand and acts as a RNA copy of the sense strand.
    • Prokaryotes have uninterrupted gene sections, no processing needed.
    • Eukaryotes have interrupted gene sections, requiring modifications after transcription.
    • In eukaryotic cells, a promoter region identifies the DNA strand as anti-sense.
    • Promoter is a short DNA sequence enabling RNA polymerase to attach.
    • RNA polymerase attaches to the promoter and opens the DNA to begin transcription.
    • Ribonucleoside triphosphates use hydrogen bonds and base pairings to build the new RNA strand.
    • RNA polymerase also brings energy for building.
    • Transcription bubble moves from the promotor area to the terminator region.
    • Terminators detach RNA polymerase from the DNA, now refered to as mRNA.
    • Splicing in eukaryotes removes noncoding regions (introns) from the mRNA.

    Translation

    • Codons within mRNA are used to create proteins.
    • Translation changes the DNA language into protein language and occurs in a 5' to 3' direction.
    • 64 possible codons, 3 have no tRNA anticodon (stop codons).
    • Start codon (AUG) signals beginning of polypeptide chain, codes for methionine.
    • Initiation: start codon (AUG) is at 5' end of mRNA, tRNA attaches to it (methionine).
    • Small ribosomal unit attaches to mRNA, looking for start codon.
    • Large ribosomal unit combines with the small one to form a translation initiation complex.
    • Initiation factors require GTP for attachment of the initiation complex.
    • Elongation: tRNA brings amino acids to the ribosome and a codon.
    • Elongation Factors assist in binding to the A site.
    • Ribosomes catalyze formation of peptide bonds (adjacent amino acids joined).
    • Ribosomes move along mRNA, translating codons to protein/polypeptides.
    • Polysome is a mRNA ribosome structure.
    • Each tRNA brings a specific amino acid, attaching to A site, translocation to P site.
    • Empty tRNA moves to the E site.
    • Termination: stop codon appears in the A site.
    • Release factor binds to the A-site.
    • Hydrolysis of the bond linking tRNA to the polypeptide chain frees the polypeptide.
    • Ribosome splits and separates from the mRNA.

    Mutations

    • Chromosomal mutations: Homologous pairs don't divide evenly during mitosis and meiosis, result in more or fewer chromosomes (46).
    • Gene mutations: Permanent changes in the DNA sequence of a gene.
      • Point mutation: One base pair is changed.
      • Frameshift mutation: A base is inserted or deleted, altering the reading frame of the gene.
    • Gene mutations can be beneficial or non-beneficial.
    • Examples of mutations include sickle-cell anemia, cystic fibrosis, Tay-Sachs disease, and Down syndrome.

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    Description

    This quiz covers crucial concepts of DNA replication and transcription. Understand the processes involved in DNA replication, including the roles of various enzymes and the semi-conservative model. Additionally, explore how RNA transcription occurs within the nucleus to transport genetic information.

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