Nucleic Acid Biochemistry — Flashcards

Flashcard 71: Restriction endonucleases are present only in cells that also have a companion enzyme that site-specifically _____ the host DNA

Answer: methylates

Flashcard 72: Which codons serve as chain terminators in mitochondria?_____

Answer: AGA and AGG

Flashcard 73: The miRNA gene present in the nucleus is transcribed to _____ miRNA

Answer: primary

Flashcard 74: Which nitrogenous base contains an amino group on the 6th C-atom?_____

Answer: Adenine

Flashcard 75: Leading strand synthesis is carried out by DNA polymerase _____.

Answer: DNA polymerase ε (epsilon)

Extra: In eukaryotes: - **DNA polymerase ε (epsilon)**: Leading strand synthesis. - **DNA polymerase δ (delta)**: Lagging strand synthesis. In prokaryotes (e.g., *E. coli*), **DNA polymerase III** is responsible for both leading and lagging strand synthesis.

Flashcard 76: Which enzyme is an alternative pathway for conversion of Adenine to AMP via the salvage pathway?_____

Answer: Adenine phosphoribosyltransferase (not HGPRT)

Flashcard 77: What products are formed by the catabolism of cytosine and uracil?

Answer: β-alanine, CO2, and NH3

Flashcard 78: 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 79: Unwinding /Denaturation of DNA is started by _____

Answer: Ori-binding protein.

Flashcard 80: Which nitrogenous base contains a methyl group on the 5th C-atom?_____

Answer: Thymine