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?

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

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

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

What is the role of CELF proteins in alternative splicing?

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

What is the outcome of alternative splicing?

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

Which factor influences the order of intron elimination?

All of the above (D) Signup and view all the answers

What is the primary transcript in RNA processing?

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

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

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

What is the consequence of the spliceosome not acting canonically?

Alternative splicing (D) Signup and view all the answers

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

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

What is the general direction of intron elimination?

From 5' to 3' (A) 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?

The protein is truncated (A) Signup and view all the answers

What is the effect of efficient co-transcriptional splicing?

Absence of primary transcript (C) Signup and view all the answers

What is the typical mechanism of alternative splicing?

Utilization of alternative exons (A) Signup and view all the answers

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

Gene expression levels (C) Signup and view all the answers

Why is the rapid elimination of introns not always observed?

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

What is the result of regulated splicing?

Production of different proteins from a single gene (B) 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?

The protein is extended (D) Signup and view all the answers

What is the purpose of alternative splicing in eukaryotic organisms?

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

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

The protein is truncated (C) Signup and view all the answers

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

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

What is the role of nucleosomas in alternative splicing?

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

What is the effect of high polymerase velocity on splicing?

It increases the skipping of exons (B) Signup and view all the answers

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

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

Why are some introns not perfect?

They have weak splicing sites (C) Signup and view all the answers

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

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

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

It influences the recognition of splicing sites (C) Signup and view all the answers

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

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

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

It increases the inclusion of exons (A) Signup and view all the answers

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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Description

This quiz covers the mechanisms of alternative splicing, including exon skipping, alternative promoter usage, and intron retention. Learn how splicing factors and regulatory elements affect alternative splicing patterns and how they are regulated. Test your knowledge of the different types of alternative splicing and their effects on gene expression.