Transcription & Translation MCAT Practice Question
A 34-year-old man presents with developmental delay, intellectual disability, and recurrent infections. Genetic testing reveals a mutation in the CDK9 gene, which encodes a catalytic subunit of P-TEFb (positive transcription elongation factor b). This complex is essential for phosphorylating DSIF and NELF, allowing release of paused RNA polymerase II during the transition from initiation to productive elongation. Which of the following best explains the pathophysiologic mechanism underlying this patient's clinical presentation?
Answer choices
- AAccumulation of paused RNA polymerase II at gene promoters with reduced synthesis of full-length transcriptsCorrect answer
- BIncreased transcription of cryptic promoters in intergenic regions due to loss of elongation control
- CEnhanced recruitment of RNA polymerase II to chromatin but decreased histone acetylation at coding sequences
- DFailure of pre-mRNA splicing machinery to assemble, resulting in nuclear retention of nascent transcripts
- EPremature termination of transcription followed by degradation of transcripts via nonsense-mediated decay
- FConstitutive activation of NELF and DSIF leading to excessive phosphorylation of the RNA polymerase II C-terminal domain
See the full explanation
Get the correct-answer rationale, why each distractor is wrong, the underlying mechanism, and high-yield associations — plus adaptive practice that targets your weak areas — with a free MedBoardPRO account.