Molecular Biology and Genomics — Flashcards

Flashcard 21: One post-transcriptional modification is the _____ of introns

Answer: splicing out

Flashcard 22: In **Nonhomologous End Joining (NHEJ)**, dsDNA breaks are recognized by the **_____** heterodimer, which then recruits the **Artemis** nuclease and other proteins to help repair the damage.

Answer: Ku70/80

Extra: NHEJ is a pathway that repairs double-strand breaks in DNA without a homologous template. Unlike Homologous Recombination, it does not require a sister chromatid and is active throughout the cell cycle (especially G1). **Key components:** 1. **Ku70/80**: Recognizes and binds to broken DNA ends. 2. **DNA-PKcs**: Recruited by Ku proteins to form the DNA-PK complex. 3. **Artemis**: A nuclease recruited and phosphorylated by DNA-PKcs to "clean up" or process the DNA ends. 4. **DNA Ligase IV & XRCC4**: Perform the final ligation. **Clinical Correlate:** Defects in NHEJ (e.g., Artemis mutations) can lead to **SCID** (because V(D)J recombination requires NHEJ) and increased sensitivity to ionizing radiation.

Flashcard 23: The promoter is an AT-rich upstream sequence with _____ and CAAT boxes

Answer: TATA

Flashcard 24: In the second step of PCR, _____ anneal to specific sequences on each DNA strand to be amplified

Answer: DNA primers

Flashcard 25: Pre-miRNA undergoes trimming by the enzyme complex _____ into mature single-stranded miRNA in the cytoplasm

Answer: DICER

Flashcard 26: The CFTR gene encodes an _____-gated Cl- channel

Answer: ATP

Flashcard 27: _____ is a tumor suppressor gene that encodes a transcription factor which regulates urogenital development

Answer: WT1

Flashcard 28: The _____ stain enters cells and stains nucleic acids

Answer: Giemsa

Flashcard 29: Proto-oncogenes are essential for cell _____ and differentiation

Answer: growth

Flashcard 30: Which forms of DNA repair repairs double-stranded breaks (due to ionizing radiation)?_____ and homologous recombination

Answer: Nonhomologous end joining