T.1 5 Introducción: corte de intrones y empalme de exones (splicing)

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Questions and Answers

What is the primary function of introns in DNA?

To replicate DNA

To separate exons (correct)

To code for proteins

To regulate gene expression

Which complex catalyzes the process of exon ligation?

Ligase

Ribosome

Helicase

Spliceosome (correct)

What is the primary mechanism by which alternative splicing generates multiple mRNA isoforms?

By changing the reading frame

By including or excluding specific introns

By modifying exon-intron boundaries

By including or excluding specific exons (correct)

Which snRNP recognizes the 3' splice site?

U2 snRNP Signup and view all the answers

What is the dynamic complex that assembles on the pre-mRNA during splicing?

Spliceosome Signup and view all the answers

What is the primary function of the U1 snRNP in splice site recognition?

To recognize the 5' splice site Signup and view all the answers

What was the initial observation that led to the discovery of introns?

The formation of a incomplete hybridization structure between mature and newly transcribed RNA Signup and view all the answers

What is a characteristic feature of introns?

They are internal sequences eliminated during splicing Signup and view all the answers

What is the term for the remaining RNA sequences after splicing?

Exons Signup and view all the answers

In which type of organism were introns first detected?

Viruses Signup and view all the answers

What is the process of eliminating internal RNA sequences and joining the remaining fragments?

Splicing Signup and view all the answers

In which type of organisms or cells can introns be found?

Some tRNAs, viruses, and eukaryotic organisms Signup and view all the answers

What is the term for the process of joining exons?

Ligation Signup and view all the answers

What is the result of splicing in terms of RNA structure?

A continuous RNA sequence Signup and view all the answers

What was the observation that led researchers to suspect the presence of introns?

An incomplete hybridization structure between mature and newly transcribed RNA Signup and view all the answers

What is the approximate percentage of the sequence that introns can represent in some genes?

99% Signup and view all the answers

What is thought to be the advantage of having introns in genes?

Greater versatility in gene expression Signup and view all the answers

Which type of intrones are typically found in mitochondrial genes of fungi and yeast?

Type I Signup and view all the answers

What is the outcome of the splicing process in terms of the original transcript length?

The mature transcript is shorter than the original Signup and view all the answers

What is the relationship between intron presence and gene expression?

Introns allow for greater variability in gene expression Signup and view all the answers

What is the purpose of the endonucleolytic and ligase reactions in splicing?

To splice introns from the primary transcript Signup and view all the answers

Which of the following is a potential disadvantage of having introns in genes?

Increased energy expenditure Signup and view all the answers

What is the general trend regarding intron presence in eukaryotic genes?

Almost all eukaryotic genes have introns Signup and view all the answers

What is the benefit of having introns in terms of evolutionary diversification?

Increased genetic diversity Signup and view all the answers

Study Notes

Splicing

Intron Definition

An intron is a non-coding region of DNA that is removed during splicing
Introns are intervening sequences that separate exons (coding regions)
Introns are typically longer than exons and are removed to form mature RNA

Exon Ligation

Exon ligation is the process of joining exons together after intron removal
This process is catalyzed by the spliceosome, a large ribonucleoprotein complex
Ligation occurs in a specific order, with the 5' exon being ligated to the 3' exon

Alternative Splicing

Alternative splicing is a mechanism that generates multiple mRNA isoforms from a single gene
This is achieved by including or excluding specific exons during splicing
Alternative splicing increases protein diversity and is a key mechanism for regulating gene expression

Splice Site Recognition

Splice site recognition is the process of identifying the 5' and 3' splice sites
The 5' splice site is recognized by the U1 snRNP, while the 3' splice site is recognized by the U2 snRNP
The U1 and U2 snRNPs bind to the pre-mRNA and define the exon-intron boundaries

Spliceosome Assembly

The spliceosome is a dynamic complex that assembles on the pre-mRNA
Assembly involves the recruitment of snRNPs (U1, U2, U4, U5, and U6) and other protein factors
The spliceosome undergoes conformational changes during splicing, allowing for the precise removal of introns and ligation of exons

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Description

This quiz covers the mechanisms of splicing, including intron definition, exon ligation, alternative splicing, and splice site recognition. Learn about the role of the spliceosome in removing introns and joining exons to form mature RNA. Understand how alternative splicing increases protein diversity and regulates gene expression.