Post-Transcriptional Modifications — Flashcards

Flashcard 1: RNA polymerase _____ makes tRNA and 5S rRNA

Answer: III

Flashcard 2: Which eukaryotic initiation factor (eIF) binds to the 5' cap of mRNA molecules?

Answer: eIF4E (part of the eIF4F complex)

Extra: eIF4E is the specific subunit that binds the 7-methylguanosine cap. The **eIF4F complex** consists of: - **eIF4E**: Cap-binding protein. - **eIF4A**: ATP-dependent RNA helicase. - **eIF4G**: Scaffold protein that coordinates the complex.

Flashcard 3: In the first step of alternative splicing, the primary transcript (hnRNA) combines with _____ and other proteins to form the spliceosome

Answer: small nuclear ribonucleoproteins (snRNPS)

Flashcard 4: What is the direction of RNA editing?_____

Answer: 3 to 5

Flashcard 5: Which RNA subtypes do not require capping at 5' end?_____

Answer: tRNA and rRNA

Flashcard 6: RNA primer synthesis is carried out by DNA polymerase _____.

Answer: alpha (α)

Extra: In eukaryotes, DNA polymerase alpha (α) is responsible for synthesizing the RNA primer. It has primase activity and initiates DNA replication by creating a short RNA-DNA primer before DNA polymerase delta (δ) or epsilon (ε) take over.

Flashcard 7: The initial mRNA of eukaryotes contains _____ and exons, which undergo splicing

Answer: introns

Flashcard 8: Polyadenylation of mRNA protects against degradation by _____

Answer: 3' exonucleases

Flashcard 9: Guanosine is converted to _____ via the enzyme purine nucleoside phosphorylase (purine salvage)

Answer: guanine

Flashcard 10: Hypoxanthine is converted to _____ via xanthine oxidase

Answer: xanthine