Transcription/translation US Medical PG Flashcards - Medical Study Cards
Master Transcription/translation with OnCourse flashcards. These spaced repetition flashcards are designed for medical students preparing for NEET PG, USMLE Step 1, USMLE Step 2, MBBS exams, and other medical licensing examinations.
Transcription/translation Flashcard Deck - 10 Cards
Flashcard 31: What are the characteristic features of mature eukaryotic mRNA?
Answer: Messenger RNA (mRNA)
Features: Capped (5'), Tailed (3' poly-A), and Spliced (removal of introns).
Flashcard 32: What must occur before RNA is transported out of the nucleus?
Answer: Post-transcriptional processing:
1. 5' capping (7-methylguanylate)
2. Polyadenylation (3' poly-A tail)
3. Splicing (intron removal)
Extra: Initial transcript is called **hnRNA** (heterogeneous nuclear RNA). These modifications occur in the nucleus. Only **mature mRNA** is exported to the cytoplasm for translation.
Processing provides:
- Protection from exonucleases.
- Recognition by the ribosome.
- Facilitation of nuclear export.
Flashcard 33: What is the initation signal for Poly-A polymerase?
Answer: AAUAAA
Flashcard 34: What is the template for Poly-A polymerase?
Answer: None (No template required)
Extra: Poly-A polymerase (PAP) adds the poly-A tail to the 3' end of mRNA. Unlike most polymerases (like DNA or RNA polymerase), it does not require a DNA or RNA template to add these adenine nucleotides; it instead uses ATP as the substrate.
Flashcard 35: What are three changes made to pre-mRNA before being transported out of the nucleus?
Answer: 5' 7-methylguanosine cap
3' poly-A tail
intron splicing
Flashcard 36: Where does mRNA processing occur in eukaryotes? Prokaryotes?
Answer: eukaryotes - in the nucleus
prokaryotes - no mRNA processing
Flashcard 37: What is the initial, unprocessed RNA transcript produced by RNA polymerase II called?
Answer: pre-mRNA (also known as hnRNA)
Extra: Heterogeneous nuclear RNA (hnRNA) is the precursor to mRNA. It undergoes three main processing steps in the nucleus before becoming mature mRNA:
1. 5' capping (7-methylguanosine cap)
2. Splicing (removal of introns)
3. 3' polyadenylation (Poly-A tail)
Flashcard 38: heterogenous nuclear RNA (hnRNA)
Answer: the initial, unprocessed RNA transcript
Flashcard 39: What is the mechanism of the death-cap mushroom toxin, α-amanitin?
Answer: Inhibits RNA polymerase II (at high concentrations, it also inhibits RNA polymerase III), preventing the synthesis of mRNA.
Extra: α-amanitin is a toxin found in Amanita phalloides (death cap mushrooms). It binds to RNA polymerase II, effectively blocking mRNA synthesis, which leads to liver failure. RNA polymerase I is insensitive to it.
Flashcard 40: How many RNA polymerases exist in eukaryotes? Prokaryotes?
Answer: eukaryotes - 3
prokaryotes - 1 multi-subunit complex
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