Transcription Termination and Elongation
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Questions and Answers

Which enzyme is responsible for synthesizing mRNA during transcription?

  • RNA polymerase IV
  • RNA polymerase II (correct)
  • RNA polymerase III
  • RNA polymerase I

    • What is the function of the promoter region in transcription?

  • To define where transcription of a gene begins (correct)
  • To define where translation of a gene begins
  • To define where recombination of a gene begins
  • To define where replication of a gene begins

    • What are the three most important types of RNA molecules involved in the transfer of genetic information to active protein molecules?

  • mRNA, miRNA, and piRNA
  • mRNA, lncRNA, and circRNA
  • mRNA, snRNA, and siRNA
  • mRNA, tRNA, and rRNA (correct)

    • Which of the following is NOT a characteristic of RNA compared to DNA?

    <p>Contains the base thymine</p> Signup and view all the answers

    What is the function of transcription factors in transcription?

    <p>To bind to the DNA template and determine which genes are transcribed</p> Signup and view all the answers

    Which promotor region is found 25 bases from the site of transcription?

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

    During transcription, which DNA strand is transcribed?

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

    Which of the following best describes gene expression?

    <p>The process of utilizing genetic information to produce physical traits</p> Signup and view all the answers

    What is the role of mRNA synthesis in gene expression?

    <p>To copy genetic information from DNA to RNA</p> Signup and view all the answers

    What is the role of exons in a gene?

    <p>They code for amino acids that make up the protein encoded by the gene</p> Signup and view all the answers

    What is the role of introns in a gene?

    <p>They reside within a gene but do not code for amino acids</p> Signup and view all the answers

    What is the consequence of both parents having faulty OCA2 expression?

    <p>Offspring will have non-pigmented pale usually blue eyes</p> Signup and view all the answers

    What is the genetic potential for eye color when expressed?

    <p>A single gene on chromosome 12 codes for brown eye pigment</p> Signup and view all the answers

    Which enzyme catalyzes the removal of non-coding introns from pre-mRNA?

    <p>RNA splicing</p> Signup and view all the answers

    What is the purpose of RNA splicing?

    <p>To remove introns (non-coding sequences of genes) from premRNA</p> Signup and view all the answers

    What is the role of the spliceosome in RNA splicing?

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

    What is alternative splicing?

    <p>The ability of one gene to produce multiple protein products</p> Signup and view all the answers

    What is the function of tropomyosins?

    <p>To form polymers along actin filaments</p> Signup and view all the answers

    What does RNA splicing result in?

    <p>The production of mature mRNA</p> Signup and view all the answers

    What is aberrant gene expression?

    <p>An abnormal pattern of gene activity</p> Signup and view all the answers

    What can cause aberrant RNA splicing?

    <p>Mutated splicing machinery and mutated splice sites</p> Signup and view all the answers

    What happens during RNA processing?

    <p>Introns are excised and exons are spliced together</p> Signup and view all the answers

    What is the purpose of adding a poly(A) tail to the mRNA?

    <p>To stabilise the mRNA molecule against cellular degradation</p> Signup and view all the answers

    What is the purpose of adding a methylated guanine cap to the 5' end of the mRNA?

    <p>To allow efficient mRNA translation</p> Signup and view all the answers

    What is the purpose of splicing in the pretranslational processing of the mRNA primary transcript?

    <p>To remove introns (non-coding sequences)</p> Signup and view all the answers

    What is the term used to describe the mRNA that has been transcribed up to a certain point?

    <p>PremRNA or primary transcript mRNA</p> Signup and view all the answers

    What is the function of the primary transcript mRNA?

    <p>To be processed into mature mRNA before translation can occur</p> Signup and view all the answers

    What is the size range of mRNA in the cell?

    <p>500-6000 nucleotides</p> Signup and view all the answers

    What is the purpose of RNA polymerase 2?

    <p>to synthesise the primary mRNA transcripts</p> Signup and view all the answers

    Which transcription factor is found 70 to 80 nucleotides from the start site?

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

    Which transcription factor is found anywhere in the regions before transcription?

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

    In what order do the transcription steps occur?

    <p>Initiation, Elongation, Termination</p> Signup and view all the answers

    When does elongation finish?

    <p>When Poly II hits an uninterrupted sequence of thymidine residues (polyT)</p> Signup and view all the answers

    What is the difference between Initiation and Elongation?

    <p>Initiation has local unwinding of the DNA to prepare for transcription and has binding of RNA polymerase 2 to a promotor sequence. Elongation is when RNA poly II uses incoming ribonucleotides to form the new mRNA strand.</p> Signup and view all the answers

    RNA polymerase II uses incoming (blank) to form the new mRNA strand.

    Signup and view all the answers

    The (blank) strand is when only the 3' to 5' DNA strand is transcribed.

    Signup and view all the answers

    The sense strand or non-template strand of the parent double helix molecule has the same sequence as the mRNA, called the (blank) strand.

    Signup and view all the answers

    What is the result of Poly II hitting an uninterrupted sequence of poly(T) on the template stand?

    <p>Termination of Pol II activity and final separation of DNA:mRNA helix formed during elongation.</p> Signup and view all the answers

    What is the primary transcript?

    <p>The new mRNA that was formed and separated from the DNA:mRNA helix.</p> Signup and view all the answers

    What is polyadenylation?

    <p>The addition of a poly(A) tail to the 3' end of the mRNA.</p> Signup and view all the answers

    What does polyadenylation do?

    <p>stabilises RNA as RNA is a lot more unstable than DNA.</p> Signup and view all the answers

    What is 5' capping?

    <p>The addition of a methylated guanine cap to the 5' end of mRNA.</p> Signup and view all the answers

    What is the purpose of splicing?

    <p>To allow the genetic sequence of a single pre-MRNA to code for many different proteins. It involves removal of introns and joining together of exons</p> Signup and view all the answers

    What process allows for removal of introns?

    <p>spliceosome excision</p> Signup and view all the answers

    What process allows joining together of exons?

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

    Study Notes

    Key Enzymes and Processes in Transcription

    • RNA polymerase is responsible for synthesizing mRNA during transcription.
    • Transcription factors facilitate the binding of RNA polymerase to the promoter region, essential for gene transcription initiation.
    • RNA splicing is catalyzed by spliceosomes, which remove non-coding introns from pre-mRNA and join exons together.

    Promoter Region and Gene Expression

    • The promoter region is crucial for starting transcription, typically located about 25 bases upstream of the transcription start site.
    • Exons are the coding sequences in a gene that will be expressed in proteins, while introns are non-coding regions that are removed during RNA processing.

    Types of RNA and Their Functions

    • Three main types of RNA involved in gene expression are:
      • mRNA (messenger RNA): conveys genetic information from DNA to synthesize proteins.
      • tRNA (transfer RNA): transports amino acids to ribosomes during protein synthesis.
      • rRNA (ribosomal RNA): forms the core of ribosome's structure and catalyzes protein synthesis.

    Characteristics of RNA

    • RNA is typically single-stranded, contains ribose sugar, and has uracil instead of thymine, distinguishing it from DNA.
    • Aberrant gene expression refers to the irregular activation or synthesis of specific genes, often resulting from mutations or environmental factors.

    RNA Processing and Modifications

    • RNA processing involves several steps, including RNA splicing, capping, and polyadenylation.
    • A poly(A) tail is added to the 3' end of the mRNA to enhance its stability and facilitate transport out of the nucleus.
    • A methylated guanine cap is added to the 5' end of mRNA for protection from degradation and aid in ribosome binding during translation.

    Transcription Steps and Elongation

    • Transcription occurs in three main stages: initiation, elongation, and termination.
    • Elongation finishes when RNA polymerase reaches a termination signal in the DNA sequence.
    • The difference between initiation and elongation lies in the phase of transcription, where initiation involves starting the transcription process, and elongation extends the mRNA strand.

    Genetic Implications and Eye Color

    • Faulty OCA2 expression in both parents can lead to a reduced potential for normal pigmentation and variation in eye color.
    • Genetic potential for eye color is influenced by multiple genes, with OCA2 being significant in determining pigment levels.

    Alternative Splicing

    • Alternative splicing allows for the generation of multiple protein variants from a single gene by rearranging different combinations of exons.
    • This process increases the diversity of proteins and is regulated by specific splicing factors.

    Structure of mRNA

    • The primary transcript mRNA represents the unprocessed RNA produced right after transcription, containing both introns and exons.
    • The size range of mRNA in cells is generally between 500-10,000 nucleotides, varying based on the gene being expressed.

    Functional Roles in Cells

    • Tropomyosins are proteins that regulate muscle contraction and stabilize actin filaments in the cytoskeleton.
    • The sense strand or non-template strand of DNA has the same sequence as mRNA, referred to as the coding strand.

    Final Notes

    • Polyadenylation is the process of adding a poly(A) tail to mRNA, crucial for mRNA stability and regulation.
    • 5' capping serves to protect mRNA from degradation and plays a role in the initiation of translation.

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    Description

    Test your knowledge on transcription termination and elongation in this quiz. Learn about the role of the sense strand and the formation of polyT and polyA tails.

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