Molecular Biology Quiz: Gene Function & Structure
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Questions and Answers

What is the primary function of telomeres in non-coding DNA sequences?

  • To code for proteins
  • To protect against chromosomal deterioration (correct)
  • To regulate RNA polymerase binding
  • To differentiate individuals
  • Which component of a gene is responsible for initiating transcription?

  • Terminator
  • Intron
  • Coding sequence
  • Promoter (correct)
  • During RNA processing, which non-coding regions are removed from the RNA transcript?

  • Exons
  • Introns (correct)
  • Telomeres
  • Promoters
  • In what direction does transcription occur?

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

    What role do gene regulatory sequences play in the transcription process?

    <p>They regulate transcription by affecting RNA polymerase binding</p> Signup and view all the answers

    Which part of a gene signals the end of transcription?

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

    Which RNA molecule is involved in bringing amino acids to the ribosome during protein synthesis?

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

    What percentage of the human genome is made up of protein-coding genes?

    <p>1.5%</p> Signup and view all the answers

    What process is crucial for the functionality of proteins like insulin?

    <p>Post-translational modifications</p> Signup and view all the answers

    What is the primary role of ubiquitin in protein metabolism?

    <p>Tagging proteins for degradation</p> Signup and view all the answers

    How do proteasomes contribute to cellular function?

    <p>By degrading unneeded proteins</p> Signup and view all the answers

    What initiates the process of protein degradation by the proteasome?

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

    Which component of the proteasome controls access to the proteolytic core?

    <p>α-subunit gate</p> Signup and view all the answers

    What is the primary purpose of the 5'-end cap added during the capping process?

    <p>To protect RNA from degradation</p> Signup and view all the answers

    Which post-transcriptional modification involves adding a poly-A tail to the RNA transcript?

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

    What is a consequence of alternative splicing in eukaryotic cells?

    <p>It allows the production of different protein variants from a single gene.</p> Signup and view all the answers

    Which of the following is NOT a major post-transcriptional event in eukaryotic cells?

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

    Why do prokaryotes not undergo post-transcriptional modifications?

    <p>They lack introns in their genes.</p> Signup and view all the answers

    What purpose does RNA splicing serve in the maturation of mRNA?

    <p>It removes non-coding sequences from the RNA transcript.</p> Signup and view all the answers

    What role does polyadenylation play regarding RNA stability?

    <p>It increases RNA stability.</p> Signup and view all the answers

    Which of the following statements accurately describes the chemical diversity of amino acids?

    <p>The side chains of amino acids determine their chemical properties.</p> Signup and view all the answers

    What nucleotide sequence marks the starting point of translation?

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

    Which site of the ribosome is where the tRNA carrying the growing peptide chain is located during elongation?

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

    During which phase of translation do release factors bind to the mRNA?

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

    What is the primary structure of a protein dependent on?

    <p>Covalent peptide bonds between adjacent amino acids</p> Signup and view all the answers

    What stabilizes the secondary structure of proteins, such as α-helices and β-pleated sheets?

    <p>Hydrogen bonds between non-adjacent amino acids</p> Signup and view all the answers

    What happens to the tRNA in the P site after it has transferred its amino acid during elongation?

    <p>It is deacylated and exits the ribosome</p> Signup and view all the answers

    Which phase of translation involves the ribosome moving along the mRNA?

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

    How does the primary structure influence the overall protein folding?

    <p>By dictating R group interactions that affect folding</p> Signup and view all the answers

    What is the primary characteristic of the tertiary structure of proteins?

    <p>It is the 3D shape determined by interactions between the R groups.</p> Signup and view all the answers

    Which type of bond is NOT involved in stabilizing the tertiary structure of proteins?

    <p>Peptide bonds</p> Signup and view all the answers

    What defines the quaternary structure of a protein?

    <p>The association of multiple polypeptide chains.</p> Signup and view all the answers

    Which description best fits globular proteins?

    <p>Spherical and typically soluble in water.</p> Signup and view all the answers

    Which is a key feature of fibrous proteins?

    <p>They provide strength and stability through a repetitive amino acid sequence.</p> Signup and view all the answers

    How is the specificity of an enzyme's active site determined?

    <p>By the precise 3D shape of the tertiary structure.</p> Signup and view all the answers

    Which protein demonstrates a conjugated quaternary structure?

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

    What role do hydrophobic interactions play in protein structure?

    <p>They cause non-polar amino acids to avoid water.</p> Signup and view all the answers

    What is the main structural role of collagen in tissues?

    <p>To provide mechanical strength and stability</p> Signup and view all the answers

    How do polar and non-polar amino acids affect protein folding?

    <p>They influence the stability of the protein by affecting solubility</p> Signup and view all the answers

    What type of amino acids would likely be found on the surface of integral membrane proteins?

    <p>Polar amino acids to form hydrophilic channels</p> Signup and view all the answers

    Which of the following is NOT a type of post-translational modification?

    <p>Phase separation</p> Signup and view all the answers

    What is the effect of glycosylation on proteins?

    <p>It influences protein stability and biological activity</p> Signup and view all the answers

    What happens to preproinsulin during its conversion to proinsulin?

    <p>A disulfide bridge is formed between A and B chains</p> Signup and view all the answers

    Which type of protein is primarily involved in enzyme catalysis and hormonal regulation?

    <p>Globular proteins</p> Signup and view all the answers

    How are disulfide bridges formed in proteins?

    <p>By covalent bonding between cysteine residues</p> Signup and view all the answers

    Study Notes

    Non-Coding DNA Sequences

    • Non-coding DNA makes up most of the human genome (about 98.5%), not directly coding for proteins.
    • Satellite DNA (short tandem repeats) is used in DNA profiling to identify individuals.
    • Telomeres are repetitive sequences at chromosome ends, protecting against deterioration during replication.
    • Introns are non-coding regions within eukaryotic genes, removed during RNA processing.
    • Non-coding genes (e.g., tRNA, rRNA) produce functional RNA molecules that don't encode proteins.
    • Gene regulatory sequences (enhancers and silencers) control transcription by influencing RNA polymerase binding.

    Gene Structure

    • A gene comprises three main sections: promoter, coding sequence, and terminator.

    Promoter

    • The promoter is a non-coding DNA sequence upstream of a gene.
    • It acts as a binding site for RNA polymerase.
    • It is regulated by transcription factors to either activate or repress RNA polymerase binding.

    Coding Sequence

    • The coding sequence is the part of the gene transcribed into RNA.
    • The RNA transcript is complementary to the DNA, except uracil (U) replaces thymine (T).

    Terminator

    • The terminator sequence signals the end of transcription.
    • Transcription termination mechanisms differ between prokaryotes and eukaryotes.

    Directionality of Transcription

    • Transcription proceeds in a 5' to 3' direction.
    • RNA polymerase adds RNA nucleotides to the 3' end of the growing mRNA strand.
    • Directionality depends on DNA orientation and RNA polymerase activity.

    Post-Transcriptional Modifications in Eukaryotes

    • Eukaryotic cells modify their RNA after transcription.
    • Three major types of modifications include: capping, polyadenylation, and splicing.

    Capping

    • Methylation occurs at the 5' end of the RNA transcript.
    • This protects the RNA from degradation and facilitates recognition by the translational machinery.

    Polyadenylation

    • Addition of a poly-A tail (adenine nucleotides) to the 3' end of the RNA transcript.
    • Increases RNA stability and aids in RNA export.

    Splicing

    • Removal of introns (non-coding sequences) and joining of exons (coding sequences) to form mature mRNA.
    • Alternative splicing allows for multiple protein variants to be produced from a single gene.

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    Description

    Test your knowledge on the critical roles of non-coding DNA, transcription mechanisms, and RNA processing. This quiz covers essential concepts such as telomeres, gene regulatory sequences, and the nature of protein-coding genes in the human genome. Challenge yourself to understand the intricacies of molecular biology!

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