Protein Synthesis & One Gene Hypothesis
95 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What primarily determines the secondary and tertiary structures of a protein?

  • The number of polypeptide chains involved
  • The presence of a quaternary structure
  • The sequence of nucleotides in DNA
  • The amino acid sequence of the protein (correct)

    • What are the two common secondary structures found in proteins?

  • Collagen fibers and alpha helical coils
  • Beta pleated sheets and alpha helices (correct)
  • Tertiary coils and disulfide bridges
  • Polypeptide chains and functional domains

    • Which statement about codons is true?

  • Codons can only include the bases A, C, and U
  • A codon is a sequence of three nucleotides (correct)
  • Each codon consists of two nucleotides
  • There are only 16 possible codons in mRNA

    • What is the minimum number of nucleotides required to encode a single amino acid?

    <p>Three nucleotides</p> Signup and view all the answers

    What structural feature primarily results from the association of two or more polypeptide chains?

    <p>Quaternary structure</p> Signup and view all the answers

    How many possible codons are there when utilizing a triplet code?

    <p>64 possible codons</p> Signup and view all the answers

    Which feature of the genetic code was confirmed using mutations in bacteriophages?

    <p>It is a triplet code</p> Signup and view all the answers

    What are domains in the context of protein structure?

    <p>Discrete functional units within a protein</p> Signup and view all the answers

    What structure does the 3' end of mRNA form during translation initiation in eukaryotes?

    <p>Closed loop</p> Signup and view all the answers

    What unique feature do some eukaryotic mRNAs possess that allows ribosome binding without a 5' cap?

    <p>Internal ribosome entry sites</p> Signup and view all the answers

    Which of the following initiates translation in bacteria?

    <p>Shine-Dalgarno sequence</p> Signup and view all the answers

    In which site of the ribosome does the initiator tRNA first occupy during elongation?

    <p>P site</p> Signup and view all the answers

    What is the role of elongation factor Tu (EF-Tu) during translation elongation?

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

    What determines the starting point of translation on an mRNA molecule?

    <p>Standard AUG start site</p> Signup and view all the answers

    Which of the following can affect the translation of downstream genes?

    <p>Upstream open reading frames (uORFs)</p> Signup and view all the answers

    What is the primary role of GTP during the elongation phase of translation?

    <p>Providing energy for tRNA binding</p> Signup and view all the answers

    What was the primary conclusion from Srb and Horowitz's research regarding the amino acid arginine's biochemical pathway?

    <p>Mutations in different groups affect different steps.</p> Signup and view all the answers

    What role do tRNAs play in protein synthesis?

    <p>They act as adapter molecules that transport amino acids to ribosomes.</p> Signup and view all the answers

    What allows group I and group II mutants to grow when citrulline is added?

    <p>They are capable of converting citrulline into arginine.</p> Signup and view all the answers

    What are isoaccepting tRNAs?

    <p>Different tRNAs that accept the same amino acid with different anticodons.</p> Signup and view all the answers

    Which statement correctly describes the effect of adding ornithine to the medium?

    <p>Group I mutants can grow, while group II and III cannot.</p> Signup and view all the answers

    How does wobble affect codon-anticodon pairing?

    <p>It enables one anticodon to pair with multiple codons.</p> Signup and view all the answers

    Which of the following represents a key feature of codon pairing?

    <p>The pairing follows the Watson-and-Crick rules.</p> Signup and view all the answers

    What does the inability of group III mutants to grow with citrulline suggest?

    <p>Their mutation affects the conversion of citrulline to arginine.</p> Signup and view all the answers

    How many sense codons are there typically in the genetic code?

    <p>61</p> Signup and view all the answers

    Which pathway step is blocked for group II mutants?

    <p>Conversion of ornithine into citrulline.</p> Signup and view all the answers

    What underlying principle is illustrated by the inability of an auxotrophic mutant to grow on certain compounds?

    <p>They can synthesize compounds after the block with proper precursors.</p> Signup and view all the answers

    In the context of tRNA, what does the term 'wobble' refer to?

    <p>The non-standard base pairing possible at the third position of codon.</p> Signup and view all the answers

    What is the key limitation of the procedure used to identify pathway steps?

    <p>It can only identify steps that produce tested compounds.</p> Signup and view all the answers

    What is the main conclusion about codon overlapping in the genetic code?

    <p>Codons typically do not overlap with each other.</p> Signup and view all the answers

    Which codon pairs with the anticodon sequence 'GAA'?

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

    What metabolic change occurs in group I mutants?

    <p>They prevent the initial conversion of precursors to ornithine.</p> Signup and view all the answers

    What role does initiation factor 3 (IF-3) play during the initiation of translation?

    <p>It prevents the large ribosomal subunit from binding.</p> Signup and view all the answers

    Where on the mRNA does the ribosome bind during the initiation of translation?

    <p>Within the 5' untranslated region</p> Signup and view all the answers

    What is the importance of the Shine-Dalgarno sequence in the initiation of translation?

    <p>It ensures proper binding of the mRNA to the ribosome.</p> Signup and view all the answers

    What is formed when the small ribosomal subunit, mRNA, and initiator tRNA with its amino acid are together?

    <p>30S initiation complex</p> Signup and view all the answers

    What happens to GTP during the initiation of translation?

    <p>It is hydrolyzed to GDP after the large subunit joins.</p> Signup and view all the answers

    Which factor is responsible for attaching the initiator tRNA to the initiation codon?

    <p>IF-2</p> Signup and view all the answers

    What occurs first in the steps of translation initiation?

    <p>Binding of the mRNA to the small ribosomal subunit</p> Signup and view all the answers

    What is the length of the mRNA region covered by the ribosome during initiation?

    <p>30 to 40 nucleotides</p> Signup and view all the answers

    What enzymatic activity is responsible for the formation of a peptide bond during elongation?

    <p>rRNA as a ribozyme</p> Signup and view all the answers

    During translocation, what occurs to the tRNA that was in the A site?

    <p>It moves to the P site.</p> Signup and view all the answers

    What initiator tRNA behavior is considered an exception during elongation?

    <p>It does not occupy the A site.</p> Signup and view all the answers

    What role does elongation factor G (EF-G) play in the process of translocation?

    <p>It facilitates the movement of the ribosome along the mRNA.</p> Signup and view all the answers

    What happens to the tRNA that occupies the E site after translocation?

    <p>It exits the ribosome into the cytoplasm.</p> Signup and view all the answers

    Which of the following correctly summarizes the movement of tRNAs during elongation?

    <p>Cytoplasm → A site → P site → E site → Cytoplasm</p> Signup and view all the answers

    What effect does the absence of elongation factor P (EF-P) have during translation?

    <p>It causes ribosomes to stall during translation.</p> Signup and view all the answers

    What is true about the translation process based on recent research methods?

    <p>Translation is a stepwise, non-continuous process.</p> Signup and view all the answers

    What characteristic of the genetic code allows an amino acid to be encoded by multiple codons?

    <p>Degeneracy of the code</p> Signup and view all the answers

    Which of the following correctly identifies a feature of tryptophan and methionine in the context of codons?

    <p>They are encoded by a single codon.</p> Signup and view all the answers

    What did Nirenberg and Leder achieve through their experiments with synthetic mRNA?

    <p>They determined which amino acids correspond to specific codons.</p> Signup and view all the answers

    How many sense codons are there in the genetic code?

    <p>61</p> Signup and view all the answers

    What is the significance of the term 'degenerate' in the context of the genetic code?

    <p>It describes the redundancy in the coding of amino acids.</p> Signup and view all the answers

    Which two amino acids are encoded by a single codon each?

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

    How many possible codons can be formed with a triplet code using four nucleotide bases?

    <p>64</p> Signup and view all the answers

    What happens to unbound tRNAs when a mixture of short mRNAs, ribosomes, and tRNAs is filtered through a nitrocellulose filter?

    <p>They pass through the filter.</p> Signup and view all the answers

    What outcome is expected when using a 4:1 ratio of cytosine to adenine nucleotides to produce RNA?

    <p>Higher probability of codons with two Cs and one A</p> Signup and view all the answers

    Which amino acid is not produced from the poly(AC) RNAs according to the provided information?

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

    What is a limitation of the random copolymer technique in determining codon identities?

    <p>It does not provide information about the base sequence of codons</p> Signup and view all the answers

    What technique did Nirenberg and Leder develop to overcome the limitations of random copolymers?

    <p>Ribosome-bound tRNAs</p> Signup and view all the answers

    In the context of random copolymers, how is the theoretical probability of a specific codon calculated?

    <p>By considering the ratios of the nucleotides used</p> Signup and view all the answers

    What does the genetic code redundancy imply for codon specification?

    <p>One amino acid can be specified by multiple codons</p> Signup and view all the answers

    How many different codons were produced when adenine and cytosine nucleotides were mixed?

    <p>8</p> Signup and view all the answers

    Which amino acids would be produced more frequently if a codon encoded two Cs and one A?

    <p>More than those encoded by two As and one C</p> Signup and view all the answers

    What is the primary function of aminoacyl-tRNA synthetases?

    <p>They recognize specific amino acids and their corresponding tRNAs.</p> Signup and view all the answers

    Which feature at the 3' end of tRNA is critical for amino acid attachment?

    <p>The CCA sequence.</p> Signup and view all the answers

    What are the components assembled during the initiation of translation?

    <p>mRNA, ribosomal subunits, initiation factors, and initiator tRNA.</p> Signup and view all the answers

    What does the tRNA charging process require?

    <p>ATP.</p> Signup and view all the answers

    In bacterial translation, what forms the functional ribosome?

    <p>30S and 50S subunits.</p> Signup and view all the answers

    What role does guanosine triphosphate (GTP) play during initiation?

    <p>It serves as an energy source for binding initiation factors.</p> Signup and view all the answers

    Which amino acid is attached to initiator tRNA in bacteria?

    <p>N-formylmethionine.</p> Signup and view all the answers

    How is the specificity of aminoacyl-tRNA synthetases for tRNAs determined?

    <p>By the sequence of nucleotides in the tRNA.</p> Signup and view all the answers

    What is the primary function of tRNAs during protein synthesis?

    <p>To bind to amino acids and deliver them to ribosomes</p> Signup and view all the answers

    How does the wobble hypothesis affect codon pairing?

    <p>It enables one anticodon to pair with different codons</p> Signup and view all the answers

    Which position of the codon does wobble pairing affect?

    <p>Third (3') base</p> Signup and view all the answers

    What is true about the number of codons compared to tRNAs in cells?

    <p>There are more codons than tRNAs</p> Signup and view all the answers

    What does the genetic code being 'nonoverlapping' imply?

    <p>Each nucleotide is part of only one codon</p> Signup and view all the answers

    Which of the following best describes synonymous codons?

    <p>Codons that code for the same amino acid</p> Signup and view all the answers

    Which base pairing rule is satisfied by the binding of the third base of a codon to the first base of an anticodon?

    <p>A pairs with U</p> Signup and view all the answers

    What is the primary role of the cap at the 5' end of eukaryotic mRNA in translation?

    <p>To initiate the small ribosomal subunit binding</p> Signup and view all the answers

    Which of the following factors is NOT involved in the eukaryotic initiation complex formation?

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

    What is the function of the cap-binding complex (CBC) in eukaryotic mRNA?

    <p>To promote the initial round of translation</p> Signup and view all the answers

    Which of the following describes the role of initiation factors in eukaryotic translation initiation?

    <p>They facilitate the scanning of mRNA for the start codon</p> Signup and view all the answers

    What enhances the binding of the small ribosomal subunit to the mRNA during translation initiation in eukaryotes?

    <p>Interaction between poly(A) tail and 5' cap proteins</p> Signup and view all the answers

    What is the function of the poly(A) tail at the 3' end of eukaryotic mRNA?

    <p>It aids in ribosome assembly during initiation</p> Signup and view all the answers

    How does the Kozak sequence contribute to translation in eukaryotes?

    <p>It surrounds the start codon, facilitating its recognition</p> Signup and view all the answers

    What key difference exists between bacterial and eukaryotic initiation of translation?

    <p>The requirement for a poly(A) tail</p> Signup and view all the answers

    What role does the 23S rRNA play in the formation of peptide bonds during elongation?

    <p>It serves as a catalyst for peptide bond formation.</p> Signup and view all the answers

    What occurs to the ribosome during the translocation step of elongation?

    <p>It shifts to position the empty A site over the next codon.</p> Signup and view all the answers

    What happens to the tRNA that was in the A site after the translocation step?

    <p>It occupies the P site with the growing polypeptide chain.</p> Signup and view all the answers

    Which factor is responsible for the hydrolysis of GTP during the translocation process?

    <p>Elongation factor G (EF-G)</p> Signup and view all the answers

    What is the function of elongation factor P (EF-P) during translation?

    <p>To enhance translation of proteins with consecutive proline residues.</p> Signup and view all the answers

    Which of the following describes the movement of tRNAs through the ribosome during elongation?

    <p>Cytoplasm → A site → P site → E site → cytoplasm.</p> Signup and view all the answers

    What unique circumstance applies to the initiator tRNA during the elongation process?

    <p>It attaches directly to the P site and does not occupy the A site.</p> Signup and view all the answers

    What has recent research revealed about the nature of translation?

    <p>Translation does not take place in a smooth, continuous fashion.</p> Signup and view all the answers

    Study Notes

    Protein Synthesis

    • Proteins are crucial to all living processes
    • Proteins are central in chemical reactions as biological catalysts (enzymes)
    • Structural components, providing support and scaffolding in cell membranes, filaments, bone, and hair
    • Some proteins have regulatory, communication, or defense roles
    • Proteins are polymers made of amino acids linked end-to-end
    • There are 20 common amino acids in proteins, shown with three-letter and one-letter abbreviations
    • Amino acids have a similar structure, differing in R groups that dictate chemical properties

    The One Gene, One Enzyme Hypothesis

    • Archibald Garrod first suggested a relation between genotype and proteins (1908)
    • George Beadle and Edward Tatum's work in the 1940s in the bread mold Neurospora defined the relation between genotype and phenotype
    • They developed the "one gene, one enzyme hypothesis," linking genes to enzymes
    • Neurospora is a suitable model organism for studying mutations due to its ease of cultivation in the lab and its haploid vegetative parts
    • Irradiating Neurospora spores induces mutations and allows for the identification of cultures with mutations
    • The one gene, one enzyme hypothesis is a link between the genetic material and enzymes

    Biochemical Pathways and Mutations

    • Neurospora grows on minimal media containing inorganic salts, nitrogen, a carbon source (like sucrose), and biotin
    • It can synthesize all its needed biological molecules from basic compounds
    • Mutations may disrupt fungal growth if it disables the ability to synthesize essential biological molecules
    • Mutants are called auxotrophs, and they can grow on media containing the substance they cannot produce
    • Beadle and Tatum determined the specific effect of a mutation by adding different essential biological molecules to a minimal medium
    • Wild-type Neurospora grows on a minimal medium
    • Auxotrophic mutants lack the ability to synthesize a certain molecule
    • Auxotrophic mutants can grow in a medium containing the required molecule

    The Structure of Proteins

    • Proteins are complex molecules with different levels of organization
    • Primary structure: the amino acid sequence
    • Secondary structure: a 3D structure, often as a beta pleated sheet or alpha helix
    • Tertiary structure: the overall, 3D shape of the protein
    • Quaternary structure: association of multiple polypeptide chains
    • The primary structure determines the secondary and tertiary structures
    • Proteins fold into complex 3D shapes that are crucial to their function
    • Certain amino acid sequences may require some help to fold correctly
    • Molecular chaperones assist in the proper folding of proteins

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Related Documents

    Chapter 15.1: Many Genes Encode Proteins (PDF)

    Description

    Explore the essential role of proteins in living organisms and their functions as biological catalysts, structural components, and regulators. Understand Archibald Garrod's and George Beadle and Edward Tatum's contributions to the 'one gene, one enzyme hypothesis' through the study of Neurospora and its genetic implications.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser