24 Questions
What is the primary function of introns in DNA?
To separate exons
Which complex catalyzes the process of exon ligation?
Spliceosome
What is the primary mechanism by which alternative splicing generates multiple mRNA isoforms?
By including or excluding specific exons
Which snRNP recognizes the 3' splice site?
U2 snRNP
What is the dynamic complex that assembles on the pre-mRNA during splicing?
Spliceosome
What is the primary function of the U1 snRNP in splice site recognition?
To recognize the 5' splice site
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
What is a characteristic feature of introns?
They are internal sequences eliminated during splicing
What is the term for the remaining RNA sequences after splicing?
Exons
In which type of organism were introns first detected?
Viruses
What is the process of eliminating internal RNA sequences and joining the remaining fragments?
Splicing
In which type of organisms or cells can introns be found?
Some tRNAs, viruses, and eukaryotic organisms
What is the term for the process of joining exons?
Ligation
What is the result of splicing in terms of RNA structure?
A continuous RNA sequence
What was the observation that led researchers to suspect the presence of introns?
An incomplete hybridization structure between mature and newly transcribed RNA
What is the approximate percentage of the sequence that introns can represent in some genes?
99%
What is thought to be the advantage of having introns in genes?
Greater versatility in gene expression
Which type of intrones are typically found in mitochondrial genes of fungi and yeast?
Type I
What is the outcome of the splicing process in terms of the original transcript length?
The mature transcript is shorter than the original
What is the relationship between intron presence and gene expression?
Introns allow for greater variability in gene expression
What is the purpose of the endonucleolytic and ligase reactions in splicing?
To splice introns from the primary transcript
Which of the following is a potential disadvantage of having introns in genes?
Increased energy expenditure
What is the general trend regarding intron presence in eukaryotic genes?
Almost all eukaryotic genes have introns
What is the benefit of having introns in terms of evolutionary diversification?
Increased genetic diversity
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
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.
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