T.15 Splicing alternativo

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Questions and Answers

What is the result of exon skipping in the CD45 gene?

  • Regulation of transcriptional initiation
  • Inclusion of premature stop codons in the final mRNA transcript
  • Production of different protein isoforms with distinct functions (correct)
  • Production of a single protein isoform

What is the mechanism by which the human calcitonin gene produces different transcripts in different tissues?

  • Alternative promoter usage (correct)
  • Exon skipping
  • Splicing factor regulation
  • Intron retention

At which levels can alternative splicing be regulated?

  • Transcriptional, post-transcriptional, and epigenetic levels (correct)
  • Epigenetic level only
  • Post-transcriptional level only
  • Transcriptional level only

What is the function of splicing factors in alternative splicing?

<p>To bind to specific sequences in pre-mRNA to regulate alternative splicing (D)</p> Signup and view all the answers

What is the result of intron retention in the survival motor neuron 1 (SMN1) gene?

<p>Production of a truncated protein associated with spinal muscular atrophy (A)</p> Signup and view all the answers

What is the role of CELF proteins in alternative splicing?

<p>To regulate alternative splicing as a splicing factor (A)</p> Signup and view all the answers

What is the outcome of alternative splicing?

<p>Production of different messenger RNA molecules from a single gene (A)</p> Signup and view all the answers

Which factor influences the order of intron elimination?

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

What is the primary transcript in RNA processing?

<p>The initial RNA molecule before intron elimination (B)</p> Signup and view all the answers

What is the primary reason for the existence of many introns in eukaryotic genomes?

<p>To allow for the complexity of eukaryotic organisms (C)</p> Signup and view all the answers

What is the consequence of the spliceosome not acting canonically?

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

What happens to the exons that are 'skipped' during alternative splicing?

<p>They are not part of the final mRNA (D)</p> Signup and view all the answers

What is the general direction of intron elimination?

<p>From 5' to 3' (A)</p> Signup and view all the answers

What is the consequence of retaining an intron in the mature mRNA, if the intron sequence does not have a reading frame?

<p>The protein is truncated (A)</p> Signup and view all the answers

What is the effect of efficient co-transcriptional splicing?

<p>Absence of primary transcript (C)</p> Signup and view all the answers

What is the typical mechanism of alternative splicing?

<p>Utilization of alternative exons (A)</p> Signup and view all the answers

Which of the following does not affect the order of intron elimination?

<p>Gene expression levels (C)</p> Signup and view all the answers

Why is the rapid elimination of introns not always observed?

<p>Because the intron is dependent on the efficiency of the spliceosome (D)</p> Signup and view all the answers

What is the result of regulated splicing?

<p>Production of different proteins from a single gene (B)</p> Signup and view all the answers

What is the result of including an intron sequence in the mature mRNA, if the sequence has a reading frame?

<p>The protein is extended (D)</p> Signup and view all the answers

What is the purpose of alternative splicing in eukaryotic organisms?

<p>To allow for the expression of different proteins in different tissues (A)</p> Signup and view all the answers

What is the consequence of including a 'megaintron' in the mature mRNA?

<p>The protein is truncated (C)</p> Signup and view all the answers

What is the main difference between alternative splicing and RNA editing?

<p>Alternative splicing changes amino acids in the protein sequence (B)</p> Signup and view all the answers

What is the role of nucleosomas in alternative splicing?

<p>They decrease the velocity of RNA polymerase II (D)</p> Signup and view all the answers

What is the effect of high polymerase velocity on splicing?

<p>It increases the skipping of exons (B)</p> Signup and view all the answers

What is the function of 5-methylcytosine in alternative splicing?

<p>It decreases the velocity of RNA polymerase II (C)</p> Signup and view all the answers

Why are some introns not perfect?

<p>They have weak splicing sites (C)</p> Signup and view all the answers

What is the result of alternative splicing in the Drosophila axon guidance receptor?

<p>38,000 potential variants of the protein (C)</p> Signup and view all the answers

What is the role of RNA polymerase II in alternative splicing?

<p>It influences the recognition of splicing sites (C)</p> Signup and view all the answers

Why is it not possible to achieve perfect regulation with perfect introns?

<p>Perfect introns would not allow for alternative splicing (A)</p> Signup and view all the answers

What is the effect of reducing the velocity of RNA polymerase II on splicing?

<p>It increases the inclusion of exons (A)</p> Signup and view all the answers

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Study Notes

Alternative Splicing

Exon Skipping

  • A mechanism of alternative splicing where one or more exons are omitted from the final mRNA transcript
  • Can result in the production of different protein isoforms with distinct functions
  • Can be regulated by splicing factors and other trans-acting elements
  • Example: exon skipping in the CD45 gene results in different isoforms with varying cellular distributions

Alternative Promoter Usage

  • Refers to the use of different promoters to initiate transcription of the same gene
  • Can result in different first exons being included in the final mRNA transcript
  • Can be regulated by transcription factors and other cis-acting elements
  • Example: the human calcitonin gene uses alternative promoters to produce different transcripts in different tissues

Regulation of Alternative Splicing

  • Alternative splicing can be regulated at multiple levels, including transcriptional, post-transcriptional, and epigenetic levels
  • Splicing factors, transcription factors, and other regulatory elements can affect alternative splicing patterns
  • Cellular context, including cell type, differentiation state, and environmental cues, can also influence alternative splicing

Splicing Factors

  • Proteins that bind to specific sequences in pre-mRNA to regulate alternative splicing
  • Can act as activators or repressors of splicing
  • Examples of splicing factors include SR proteins, hnRNP proteins, and CELF proteins
  • Splicing factors can interact with each other and with other regulatory elements to modulate alternative splicing

Intron Retention

  • A mechanism of alternative splicing where an intron is retained in the final mRNA transcript
  • Can result in the inclusion of premature stop codons, leading to nonsense-mediated decay or the production of truncated proteins
  • Can be regulated by splicing factors and other trans-acting elements
  • Example: intron retention in the survival motor neuron 1 (SMN1) gene leads to the production of a truncated protein associated with spinal muscular atrophy

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