Regulation after transcription
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Questions and Answers

What is the primary level of gene expression control in eukaryotic cells like photoreceptors?

  • mRNA translation
  • Protein modification
  • Transcription (correct)
  • RNA processing

    • What is the function of microRNAs in gene expression?

  • To degrade mRNA or block translation (correct)
  • To add chemical groups to proteins
  • To remove amino acids from proteins
  • To increase mRNA translation

    • What is a consequence of alternative splicing of transcripts?

  • Increased mRNA translation
  • Production of different mRNAs and proteins from the same RNA transcript (correct)
  • Production of identical mRNAs and proteins
  • Decreased protein modification

    • What determines the identity and properties of a eukaryotic cell?

    <p>The types of genes the cell expresses</p> Signup and view all the answers

    At which stage can gene expression be regulated after transcription?

    <p>During RNA processing, mRNA translation, and protein modification</p> Signup and view all the answers

    What is the function of neurotransmitters in a photoreceptor cell?

    <p>To allow signals to be relayed to the brain</p> Signup and view all the answers

    What is the primary transcript produced during eukaryotic gene transcription?

    <p>pre-mRNA molecule</p> Signup and view all the answers

    What is the process of removing sections of pre-mRNA molecule called?

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

    What regulates alternative splicing in eukaryotic cells?

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

    What determines how much protein is made from an mRNA molecule?

    <p>All of the above</p> Signup and view all the answers

    What are small regulatory RNAs that control mRNA lifespan and translation?

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

    What is the function of microRNAs?

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

    How are microRNAs formed?

    <p>Transcription of a microRNA gene</p> Signup and view all the answers

    What is the result of a microRNA being perfectly complementary to an mRNA?

    <p>Cutting of the mRNA in two</p> Signup and view all the answers

    What is the term for the process of selecting different portions of an mRNA to form different variants?

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

    What is the term for the additions made to the pre-mRNA molecule to form a mature mRNA molecule?

    <p>Capping, splicing, and poly-A addition</p> Signup and view all the answers

    What is the typical outcome when the miRNA is perfectly complementary to the mRNA?

    <p>The mRNA is often cut in two by an enzyme in the protein complex.</p> Signup and view all the answers

    What is the role of the 'helper' proteins during translation initiation?

    <p>They ensure the correct positioning of the ribosome on the mRNA.</p> Signup and view all the answers

    What is the effect of phosphorylation on the activity of eukaryotic initiation factor-2 (eIF-2)?

    <p>It turns eIF-2 'off' by inducing a shape change.</p> Signup and view all the answers

    What is the purpose of regulating protein translation in a cell?

    <p>To conserve energy and resources during periods of starvation.</p> Signup and view all the answers

    What is the primary function of ubiquitin in protein regulation?

    <p>To mark proteins for degradation by the proteasome</p> Signup and view all the answers

    What is the result of phosphorylation on eIF-2?

    <p>Inactivation of translation</p> Signup and view all the answers

    What is the outcome when the miRNA and its target have some mismatches?

    <p>The RNA-protein complex binds to the mRNA and blocks translation.</p> Signup and view all the answers

    What is the common thread among phosphorylation, ubiquitination, and other post-translational modifications?

    <p>They all regulate protein activity or persistence</p> Signup and view all the answers

    What is the function of miRNAs in organisms?

    <p>To reduce the expression of their target genes.</p> Signup and view all the answers

    What is the result of inactivating translation initiation through phosphorylation of eIF-2?

    <p>The cell stops synthesizing proteins.</p> Signup and view all the answers

    Where can proteins be found in the cell after modifications such as phosphorylation?

    <p>In the nucleus, cytoplasm, or attached to the plasma membrane</p> Signup and view all the answers

    What is an example of a post-translational modification that activates a protein?

    <p>Proteolytic cleavage of the protein.</p> Signup and view all the answers

    What is the net effect of phosphorylation on protein behavior?

    <p>It varies from protein to protein, with different effects</p> Signup and view all the answers

    What is the fate of ubiquitin-tagged proteins in the cell?

    <p>They are taken to the proteasome for degradation</p> Signup and view all the answers

    What is the role of miRNAs in the development and function of the vascular system in mice?

    <p>They promote the development of the vascular system.</p> Signup and view all the answers

    What is the effect of changes in miRNA expression levels on human diseases?

    <p>They are associated with various types of cancer and cardiac hypertrophy.</p> Signup and view all the answers

    Study Notes

    Gene Expression Regulation

    • Gene expression can be regulated at various stages, including transcription, RNA processing, translation, and protein modifications.

    RNA Processing

    • Pre-mRNA undergoes modifications, including splicing, capping, and poly-A tail addition, to become a mature mRNA molecule.
    • Alternative splicing allows for different exon combinations from a single pre-mRNA, resulting in different mRNA molecules.
    • Regulatory proteins bind to specific sites on the pre-mRNA to control alternative splicing.

    Small Regulatory RNAs

    • MicroRNAs (miRNAs) are small regulatory RNAs that control mRNA lifespan and translation.
    • miRNAs bind to specific mRNAs, either blocking translation or causing mRNA degradation.
    • miRNAs play a key role in development and disease, and changes in miRNA expression are associated with cancer and cardiac hypertrophy.

    Regulation of Translation

    • Translation initiation is a key step in regulating translation, involving the binding of eukaryotic initiation factor-2 (eIF-2) to the ribosome.
    • Phosphorylation of eIF-2 acts as a switch, turning translation on or off.

    Protein Modifications

    • Proteins can be regulated after translation through removal of amino acids, addition of chemical groups, or proteolytic cleavage.
    • Chemical modifications, such as phosphorylation, can activate, deactivate, or alter protein behavior.
    • Ubiquitination tags proteins for degradation by the proteasome, controlling the persistence of a protein in the cell.

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