Molecular Biology & Genetics

Topics in this chapter

• DNA Replication and Repair
• Transcription and Gene Regulation
• RNA Processing and Post-Transcriptional Control
• Translation and Protein Synthesis
• Genetic Variation and Inherited Disorders
• Prokaryotic and Eukaryotic Molecular Biology

Practice questions

1. Question 1Q-75B511

   A 32-year-old man presents with progressive ataxia, nystagmus, and recurrent psychiatric disturbances. Genetic testing reveals an expansion of a trinucleotide repeat (CAG) in the coding region of a specific gene. Which of the following best describes the molecular consequence of this specific trinucleotide expansion?

   1. A.Transcriptional silencing due to hypermethylation of CpG islands
   2. B.Gain-of-function toxicity due to polyglutamine tract expansion in the protein
   3. C.Aberrant mRNA splicing leading to nonsense-mediated decay
   4. D.Impaired DNA mismatch repair causing microsatellite instability
   See the answer and solution
2. Question 2Q-25A197

   During DNA replication in eukaryotes, which of the following enzymes is primarily responsible for the removal of RNA primers and filling the resulting gaps on the lagging strand?

   1. A.DNA polymerase alpha-primase complex
   2. B.DNA polymerase delta with FEN1 and RNase H
   3. C.DNA polymerase gamma
   4. D.Topoisomerase II
   See the answer and solution
3. Question 3Q-E1DB33

   A researcher is studying a novel antibiotic that inhibits bacterial transcription by specifically binding to the beta subunit of RNA polymerase, preventing the formation of phosphodiester bonds after the first few nucleotides are joined. Which antibiotic is this?

   1. A.Rifampicin
   2. B.Actinomycin D
   3. C.Streptomycin
   4. D.Chloramphenicol
   See the answer and solution
4. Question 4Q-668B77

   A 4-year-old child presents with extreme photosensitivity, dry skin, and multiple pigmented spots on sun-exposed areas. A skin biopsy fibroblast culture reveals a defect in nucleotide excision repair (NER). This enzymatic defect most directly impairs the removal of which of the following?

   1. A.Pyrimidine dimers induced by ultraviolet light
   2. B.O6-methylguanine adducts caused by alkylating agents
   3. C.Double-strand breaks caused by ionizing radiation
   4. D.Mismatched bases due to replication slippage
   See the answer and solution
5. Question 5Q-375F70

   Which of the following eukaryotic translation initiation factors (eIFs) is responsible for recognizing the 7-methylguanosine cap structure of mRNA?

   1. A.eIF2
   2. B.eIF4E
   3. C.eIF4A
   4. D.eIF6
   See the answer and solution