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Questions and Answers
What is the purpose of adding the 5' guanosine triphosphate cap to pre-mRNA?
What is the purpose of adding the 5' guanosine triphosphate cap to pre-mRNA?
- It signals the start of transcription.
- It enhances the nucleotide sequence of mRNA.
- It facilitates the removal of introns.
- It aids in transporting mRNA across the nuclear membrane. (correct)
Which component is responsible for removing introns from the pre-mRNA molecule?
Which component is responsible for removing introns from the pre-mRNA molecule?
- Transcription factors
- Ribosomes
- Spliceosome (correct)
- Polyadenylation factors
How many adenine nucleotides are typically added to the 3' end of pre-mRNA during polyadenylation?
How many adenine nucleotides are typically added to the 3' end of pre-mRNA during polyadenylation?
- 100-150
- 200-250 (correct)
- 50-100
- 300-350
What is the role of exons in pre-mRNA?
What is the role of exons in pre-mRNA?
What overall effect do both the 5' cap and poly A tail have on mRNA?
What overall effect do both the 5' cap and poly A tail have on mRNA?
Flashcards
Pre-mRNA
Pre-mRNA
The initial RNA transcript produced directly from DNA transcription. It needs modifications before leaving the nucleus.
5' cap
5' cap
A modified guanine nucleotide added to the 5' end of pre-mRNA. It protects mRNA from degradation and helps it exit the nucleus.
Poly A tail
Poly A tail
A long chain of adenine nucleotides added to the 3' end of pre-mRNA. It helps stabilize mRNA and ensure its proper transport.
Exons
Exons
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Introns
Introns
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Study Notes
Transcription and RNA Processing
- Transcription produces RNA molecules from DNA, transferring genetic information.
- Messenger RNA (mRNA) serves as the template for protein synthesis.
- Pre-mRNA is the initial RNA transcript produced directly from transcription, requiring modifications before exiting the nucleus.
Post-Transcriptional Modifications
-
5' guanosine triphosphate cap:
- Added to the 5' end of pre-mRNA via a 5'-to-5' triphosphate linkage, forming a 7-methylguanosine cap.
- Protects mRNA from degradation during translation and aids in exiting the nucleus.
- Function: Increases stability and aids in transport across nuclear membrane.
-
Polyadenylation (Poly A tail):
- A series of adenine nucleotides (200-250) are added to the 3' end of pre-mRNA after a small section is removed.
- Function: Increases stability and aids in transport out of the nucleus.
-
Splicing:
- Exons: Regions of pre-mRNA that code for protein.
- Introns: Non-coding regions of pre-mRNA.
- Spliceosome: A complex of proteins and RNA that removes introns and splices exons together.
- Function: Produces the final mRNA molecule, ready for protein synthesis.
Importance of Modifications
- The 5' cap and poly A tail protect mRNA from degradation and increase its stability in the cytoplasm.
- These modifications also facilitate the movement of mRNA from the nucleus to the cytoplasm for protein synthesis.
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