Alternative Splicing in Molecular Biology
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Questions and Answers

What is the outcome of C to U editing in the context of neurofibromatosis type 1?

  • It increases tumor suppressor activity of NF1.
  • It has no effect on protein translation.
  • It enhances the function of the NF1 protein.
  • It generates a premature STOP codon in the NF1 protein. (correct)

    • Which of the following statements about RNA editing in mammals is true?

  • RNA editing does not impact neurological disorders.
  • RNA editing occurs only in non-coding regions.
  • Editing processes are rare in brain tissues.
  • RNA editing affects splicing, localization, stability, and translation. (correct)

    • What is a characteristic of neurofibromatoses?

  • They are genetic disorders that lead to tumors in nerve tissue. (correct)
  • They solely affect brain tissue.
  • They do not influence muscle function.
  • They are single medical disorders.

    • In what way does RNA editing relate to ALS (amyotrophic lateral sclerosis)?

    <p>It is associated with editing within coding regions in neurological disorders.</p> Signup and view all the answers

    What nucleotide change occurs when adenosine is edited in RNA editing?

    <p>Adenosine (A) is converted to inosine (I).</p> Signup and view all the answers

    What percentage of introns are typically removed from pre-mRNA during transcription elongation in humans?

    <p>65%</p> Signup and view all the answers

    Which of the following factors can affect alternative splicing?

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

    What is the primary role of Prp8 in the splicing process?

    <p>Maintaining the conformation of the active site</p> Signup and view all the answers

    What disease is associated with mutations in the Prp8 gene?

    <p>Retinitis pigmentosa</p> Signup and view all the answers

    How does alternative splicing influence developmental processes?

    <p>By controlling complex patterns of development</p> Signup and view all the answers

    What is a consequence of inefficient splicing of pre-mRNA?

    <p>Retention of expressed introns</p> Signup and view all the answers

    What is nonsense-mediated decay (NMD)?

    <p>The degradation of mRNA with premature stop codons</p> Signup and view all the answers

    Which statement about alternative splicing is correct?

    <p>It is a regulated process that allows for the generation of multiple protein isoforms</p> Signup and view all the answers

    What percentage of human genes undergo alternative splicing of their pre-mRNA transcripts?

    <p>95-100%</p> Signup and view all the answers

    Which of the following best describes constitutive exons?

    <p>They are regularly included in mRNA.</p> Signup and view all the answers

    How many different proteins can the Dscam gene potentially produce due to alternative splicing?

    <p>38,016 proteins</p> Signup and view all the answers

    Which statement accurately describes the role of alternate promoters in gene expression?

    <p>They can alter the transcription initiation sites, creating different isoforms.</p> Signup and view all the answers

    What is the approximate size of human exons compared to introns?

    <p>Exons are approximately 100-300 nucleotides, while introns are generally larger than thousands of nucleotides.</p> Signup and view all the answers

    What is the primary function of the spliceosome in mRNA processing?

    <p>To splice mRNA in a consistent manner through constitutive splicing.</p> Signup and view all the answers

    Which of the following accurately represents alternative splicing?

    <p>It allows for the production of multiple mRNA isoforms from a single gene.</p> Signup and view all the answers

    Which characteristic is true about pseudoexons?

    <p>They contain splice sites but are not recognized by the splicing machinery.</p> Signup and view all the answers

    What is a direct consequence of the mutations in the LMNA gene associated with Hutchinson-Gilford progeria syndrome (HGPS)?

    <p>Creation of a new 5´ splice site.</p> Signup and view all the answers

    Which of the following are effects of RNA splicing defects in the context of disease?

    <p>Improper protein production.</p> Signup and view all the answers

    What characteristic features are associated with Hutchinson-Gilford progeria syndrome (HGPS)?

    <p>Symptoms of normal aging at a young age.</p> Signup and view all the answers

    What type of mutation within the splicing code could lead to a premature aging syndrome like HGPS?

    <p>Point mutations affecting splice site sequences.</p> Signup and view all the answers

    How does a complete deletion of the LMNA gene impact an individual?

    <p>It leads to a form of muscle dystrophy.</p> Signup and view all the answers

    Which types of mutations can lead to alterations in the splicing code?

    <p>Mutations in splice site and splicing control sequences.</p> Signup and view all the answers

    What is the typical lifespan of individuals affected by Hutchinson-Gilford progeria syndrome?

    <p>Around 13 years.</p> Signup and view all the answers

    What role do splicing enhancers and silencers play in mRNA splicing?

    <p>They alter the splicing code and influence splicing outcomes.</p> Signup and view all the answers

    What metabolic pathway do cancer cells favor due to the Warburg effect?

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

    What is the role of pyruvate kinase M (PKM) in cancer metabolism?

    <p>Facilitates slow glycolysis and accumulation of upstream components</p> Signup and view all the answers

    Which process is primarily influenced by RNA editing in mammals?

    <p>Protein synthesis</p> Signup and view all the answers

    What percentage of pre-mRNAs is estimated to be edited in humans?

    <p>85%</p> Signup and view all the answers

    In which region of mRNA does RNA editing preferentially occur?

    <p>Introns and 3' untranslated region</p> Signup and view all the answers

    What is the primary consequence of alternative splicing in cancer cells?

    <p>Altered properties of cancer cells</p> Signup and view all the answers

    Which protein family is responsible for catalyzing RNA editing in mammals?

    <p>Adenosine deaminases acting on RNA (ADAR)</p> Signup and view all the answers

    What alternative pathway do cancer cells choose over aerobic respiration?

    <p>Anaerobic glycolysis</p> Signup and view all the answers

    What role do splicing activators such as SR proteins play in the splicing process?

    <p>They recruit U2AF and U1 snRNP to the splice sites.</p> Signup and view all the answers

    Which of the following statements about hnRNP proteins is correct?

    <p>They inhibit splicing by binding to intronic splicing silencers.</p> Signup and view all the answers

    Which factor is NOT involved in the regulation of alternative splicing?

    <p>Alterations in exon size during transcription.</p> Signup and view all the answers

    What is the main purpose of exon definition in splicing?

    <p>To identify which sequences are exons in the mRNA.</p> Signup and view all the answers

    How do splicing repressors like hnRNP proteins affect the spliceosome?

    <p>They interfere with protein-protein interactions necessary for splicing.</p> Signup and view all the answers

    Which of the following correctly describes intron definition?

    <p>A method where the spliceosome assembles through cross-intron interactions.</p> Signup and view all the answers

    What influences the efficiency of splice junction recognition?

    <p>The presence of weak splice sites in the mRNA.</p> Signup and view all the answers

    Changes in which factor can modify mRNA processing in the nucleus?

    <p>Cellular signaling pathways.</p> Signup and view all the answers

    Study Notes

    Alternative Splicing

    • Alternative splicing (AS) is the process where a single gene can code for multiple protein isoforms.
    • Up to 95-100% of human genes undergo alternative splicing.
    • This leads to a much greater complexity in the proteome than the genome would suggest.
    • Different types of alternative splicing events exist, including exon skipping, inclusion, alternative 5' and 3' splice sites, and intron retention.

    Splicing Code

    • The splicing code is a set of sequences and signals that control the splicing process.
    • This includes consensus sequences and binding sites for splicing factors.
    • Splicing factors (SFs) are proteins crucial in the control of the splicing process and the activation or repression of splicing.
    • Factors like SR proteins bind to splicing enhancers, and other factors like hnRNPs bind to splicing silencers.

    Splicing Machinery

    • The splicing machinery, called the spliceosome, is responsible for the removal of introns and the joining of exons.
    • The spliceosome is made up of small nuclear ribonucleoproteins (snRNPs).
    • The spliceosome recognizes splice sites through consensus sequences and the associated splicing factors.

    Factors Affecting Alternative Splicing

    • Changes in the expression of RNA binding proteins (RNABPs).
    • Changes in upstream signaling pathways.
    • Changes in the rate of transcription.
    • Nuclear concentration of RNABPs influence splicing.
    • Cellular environment such as stress can also impact RNABP activity and splicing patterns.
    • Elongation time of polymerase and length of introns affects the efficiency of splicing and affects the choice of exon joining.

    Mutations Affecting Splicing

    • Point mutations affecting RNA splicing signals can cause disease.
    • Mutations in splice sites, splicing enhancers, and silencers cause defects.
    • Such mutations can lead to exon skipping or intron inclusion, causing abnormal protein production.
    • Mutations in splicing factors or components of the spliceosome can also cause splicing defects.

    RNA Splicing Defects and Disease

    • Various diseases are associated with defects in RNA splicing.
    • Examples include retinitis pigmentosa and Hutchinson-Gilford progeria syndrome.
    • These disorders reflect the crucial role of accurate splicing in cellular function.
    • Mutations in genes controlling splicing factors can cause these diseases.

    Biological Importance of Alternative Splicing

    • AS creates diverse protein isoforms from a single gene.
    • It allows for modifications of protein-protein interactions.
    • AS has significant roles in regulating development, neurogenesis, cellular function, and response to environmental stress.
    • Example: Different isoforms of sex-lethal (SxL) factor control sex development in fruit flies.

    RNA Editing

    • RNA editing is the process of altering RNA sequences after transcription.
    • This change can affect protein production in different ways.
    • The process often occurs in non-coding RNAs and can affect the transcriptome.
    • Editing can affect gene expression by altering the sequence of the pre-mRNA and the resulting protein.
    • Example: Editing in nerve cells can alter the expression of certain receptor types, affecting neuronal function.
    • Two main classes of editing enzymes called ADARs, which are responsible for the alteration of nucleotide bases in RNA, in particular the deamination of adenosine to inosine.

    Mutations Affecting Spliceosome Components

    • Mutations affecting spliceosome components can lead to a variety of diseases.
    • Diseases that are associated with these type of mutations include spinal muscular atrophy, myotonic dystrophies, and other neurodegenerative disorders.

    Summary

    • Alternative splicing is a crucial mechanism for generating diversity in protein isoforms from a single gene.
    • This process involves the precise removal of introns and joining of exons, regulated by multiple factors.
    • Defects in splicing regulation or machinery can cause various genetic disorders.

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    UC Biologia Molecular Past Paper 2024-2025 PDF

    Description

    Explore the fascinating process of alternative splicing, where a single gene can lead to multiple protein isoforms. This quiz covers the mechanisms, types of splicing events, and the role of the splicing machinery in gene expression. Test your knowledge and understanding of the splicing code and its significance in the complexity of the proteome.

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