RNA Processing and Gene Expression
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RNA Processing and Gene Expression

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Questions and Answers

What role does the template strand of DNA play during transcription?

  • It is translated directly into protein.
  • It induces mutations in the RNA transcript.
  • It replaces the coding strand during RNA processing.
  • It serves as a template for the sequence of nucleotides in RNA. (correct)

    • How are codons in mRNA related to amino acids during translation?

  • Every codon corresponds to a stop signal in translation.
  • Each codon dictates the sequence of RNA nucleotides only.
  • Each codon specifies a particular amino acid to be added to the growing polypeptide chain. (correct)
  • Codons are read in the 3' to 5' direction.

    • What happens if codons are not read in the correct reading frame during translation?

  • The synthesis will pause until the frame is corrected.
  • Only the first codon will be translated.
  • Translation will result in a completely different protein. (correct)
  • The polypeptide will be synthesized correctly.

    • How many codons serve as signals to terminate translation?

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

    What modification is made to the 5' end of a pre-mRNA molecule?

    <p>A 5' G-cap is added</p> Signup and view all the answers

    Which statement is true regarding the genetic code?

    <p>The code is redundant, allowing more than one codon to specify an amino acid.</p> Signup and view all the answers

    Which function is NOT associated with the modifications at the ends of mRNA?

    <p>Assist in the translation of mRNA</p> Signup and view all the answers

    What is the main purpose of RNA splicing in pre-mRNA processing?

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

    What are the segments of RNA that are expressed and translated into amino acid sequences called?

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

    Which of the following statements about introns is true?

    <p>Introns are noncoding sequences in mRNA</p> Signup and view all the answers

    What is added to the 3' end of a pre-mRNA molecule?

    <p>A poly-A tail</p> Signup and view all the answers

    Which process directly results in a continuous coding sequence of mRNA?

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

    Which component is part of the pre-mRNA but not included in the mature mRNA?

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

    How many nucleotides correspond to one amino acid in the genetic code?

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

    What separates transcription from translation in eukaryotic cells?

    <p>The nuclear envelope</p> Signup and view all the answers

    What is the initial RNA transcript called before processing in eukaryotes?

    <p>Primary transcript</p> Signup and view all the answers

    What is the role of RNA in the flow of genetic information?

    <p>To act as the bridge between genes and proteins</p> Signup and view all the answers

    What are ribosomes primarily responsible for in the process of protein synthesis?

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

    What distinguishes prokaryotic translation from eukaryotic translation?

    <p>mRNA can be translated immediately after transcription in prokaryotes</p> Signup and view all the answers

    What results from the transcription of a gene?

    <p>Messenger RNA (mRNA)</p> Signup and view all the answers

    Which amino acid corresponds to the codon UUU?

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

    Which statement correctly describes the genetic code?

    <p>It is based on codons, which are triplet sequences of nucleotides.</p> Signup and view all the answers

    What does the presence of UAA or UGA in a codon indicate?

    <p>Stop codon</p> Signup and view all the answers

    For the codon CUG, what is the corresponding amino acid?

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

    Which base must be at the 5' end of a codon to form AUG?

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

    What is the role of transcription in gene expression?

    <p>Synthesis of RNA from DNA</p> Signup and view all the answers

    Which of the following codons is associated with Lysine?

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

    What does the 'universal' nature of the genetic code imply?

    <p>Common across most organisms</p> Signup and view all the answers

    Which nucleotide is not a part of any codon for coding amino acids?

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

    What process allows genes to be transplanted from one species to another?

    <p>Gene expression</p> Signup and view all the answers

    Which codon represents the start signal for protein synthesis?

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

    Which base is substituted for thymine in RNA?

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

    What is the role of RNA polymerase in transcription?

    <p>It unwinds the DNA strands and synthesizes RNA.</p> Signup and view all the answers

    What is the function of the promoter in transcription?

    <p>It is where RNA polymerase attaches.</p> Signup and view all the answers

    During transcription, which strand of DNA serves as the template for RNA synthesis?

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

    What term describes the length of DNA that is transcribed into RNA?

    <p>Transcription unit</p> Signup and view all the answers

    What process occurs after RNA transcription in eukaryotic cells?

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

    What happens to both ends of the primary RNA transcript during RNA processing?

    <p>They are usually altered.</p> Signup and view all the answers

    What is the final product of transcription in eukaryotic cells?

    <p>Messenger RNA (mRNA)</p> Signup and view all the answers

    Which phase follows the initiation of transcription?

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

    What signals the end of transcription in bacteria?

    <p>Termination sequence</p> Signup and view all the answers

    Study Notes

    RNA Processing

    • Each end of a pre-mRNA molecule is modified
      • The 5’ end receives a modified guanine nucleotide cap
      • The 3’ end gets a poly-A tail
    • These modifications:
      • Facilitate the export of mRNA from the nucleus
      • Protect mRNA from degradation by hydrolytic enzymes
      • Help ribosomes attach to the 5’ end

    Introns and Exons

    • Most eukaryotic genes and their RNA transcripts have long noncoding stretches of nucleotides that lie between coding regions
      • These noncoding regions are called intervening sequences, or introns
      • The coding regions are called exons
    • RNA splicing removes introns and joins exons, creating an mRNA molecule with a continuous coding sequence

    Transcription and Translation: Central Dogma

    • The information content of DNA is in the form of specific sequences of nucleotides
      • This leads to specific traits by dictating the synthesis of proteins
    • This process is called gene expression and it involves two major stages:
      • Transcription: synthesis of RNA under the direction of DNA
      • Translation: synthesis of a polypeptide under the direction of mRNA
    • Transcription produces messenger RNA (mRNA) which carries the code from DNA to the ribosomes
      • Ribosomes are the site of translation

    The Genetic Code

    • The instructions for assembling amino acids into proteins are encoded into DNA
    • The genetic code is a triplet code: a series of nonoverlapping, three-nucleotide words
    • Each codon specifies the amino acid to be placed at the corresponding position along a polypeptide
    • The mRNA codons are read in the 5’ to 3’ direction

    Cracking the Code

    • 61 out of 64 codons code for amino acids
    • 3 codons are stop signals to end translation
    • The genetic code is redundant, meaning more than one codon can specify a particular amino acid, but it is not ambiguous, meaning no codon specifies more than one amino acid
    • Codons must be read in the correct reading frame to produce the specified polypeptide

    Universal Genetic Code

    • The genetic code is nearly universal
      • Genes from one species can be transcribed and translated in another organism
      • This is because the genetic code is nearly identical in all organisms, from the simplest bacteria to the most complex animals

    Transcription: A Closer Look

    • Transcription is the first stage of gene expression
    • RNA synthesis is catalyzed by RNA polymerase, which pries the DNA strands apart and hooks together the RNA nucleotides
    • The RNA is complementary to the DNA template strand
    • The DNA sequence where RNA polymerase attaches is called the promoter
    • The stretch of DNA that is transcribed is called a transcription unit
    • The sequence signaling the end of transcription is called the terminator (in bacteria)

    Eukaryotic RNA Processing

    • Eukaryotic cells modify RNA after transcription
    • The primary transcript is the initial RNA transcript from any gene prior to processing
    • RNA processing involves the following modifications to the pre-mRNA:
      • 5' capping
      • 3' polyadenylation
      • Splicing

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    Genetic Code, Transcription, and Translation Notes PDF

    Description

    Explore the fascinating processes of RNA processing, including modifications such as the guanine cap and poly-A tail. Learn about the roles of introns and exons in mRNA formation and the central dogma of molecular biology that outlines gene expression. This quiz will test your understanding of these critical biological concepts.

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