Questions CNM 01_Introduction_2
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30 Questions & Answers – Based on 01_Introduction_2.pdf
1. What is the primary focus of molecular biology?
Answer: To understand cellular processes in terms of the structure and interactions of biological macromolecules, particularly DNA, RNA, and proteins.
2. How has the scope of molecular biology expanded beyond the central dogma?
Answer: It now includes gene regulation, chromatin structure, RNA processing and modifications, non-coding RNAs, protein folding, degradation, and epigenetics.
3. What is the central dogma of molecular biology?
Answer: DNA is transcribed into RNA, which is then translated into protein.
4. What are non-coding RNAs and what roles can they play?
Answer: Non-coding RNAs (like rRNA, tRNA, miRNA) are not translated into proteins but have functional roles in translation, regulation, and gene expression.
5. Why can’t RNA Polymerase II initiate transcription on its own?
Answer: It requires the help of general transcription factors (GTFs) to recognize promoter regions and assemble the pre-initiation complex.
6.
What is the function of the TATA box in transcription?
Answer: It is a DNA sequence within the promoter region that is recognized by TBP (TATA-binding protein), facilitating the assembly of the transcription machinery.
7.
Which transcription factor contains the TATA-binding protein (TBP)?
Answer: TFIID.
8.
What is the role of TFIIH in transcription initiation?
Answer: It unwinds DNA using helicase activity and phosphorylates the C-terminal domain (CTD) of RNA Polymerase II to initiate elongation.
9.
What is the pre-initiation complex (PIC)?
Answer: A complex of general transcription factors (TFIID, TFIIA, TFIIB, TFIIF, TFIIE, TFIIH) and RNA Pol II assembled at the promoter to initiate transcription.
10.
How does TFIIA contribute to transcription initiation?
Answer: It stabilizes the interaction between TBP and the DNA.
11.
What is the significance of CTD phosphorylation?
Answer: It activates RNA Polymerase II for transcription elongation and recruits RNA processing machinery (e.g., for capping, splicing, and polyadenylation).
12.
What is the direction of RNA synthesis?
Answer: 5′ to 3′.
13.
What does RNA Polymerase II require to synthesize RNA?
Answer: A DNA template, ribonucleotide triphosphates (rNTPs), and the assistance of general transcription factors.
14.
What is alternative splicing?
Answer: A process by which different combinations of exons are joined together to produce multiple mRNA variants from a single gene.
15.
What is the spliceosome made of?
Answer: A complex of small nuclear ribonucleoproteins (snRNPs) including U1, U2, U4, U5, and U6.
16.
What sequences are necessary for splice site recognition?
Answer: The 5′ splice site, the branch point A, and the 3′ splice site.
17.
Which snRNP binds the 5′ splice site?
Answer: U1 snRNP.
18.
Which snRNP recognizes the branch point A?
Answer: U2 snRNP.
19.
What is the function of the U4/U6-U5 tri-snRNP complex?
Answer: It completes the spliceosome assembly and mediates catalysis of splicing reactions.
20.
What chemical reactions occur during splicing?
Answer: Two transesterification reactions: one to cut the 5′ splice site and form a lariat, and another to cut the 3′ splice site and ligate exons.
21.
What is the outcome of successful splicing?
Answer: A mature mRNA transcript with exons ligated and introns removed.
22.
How does alternative splicing increase proteomic diversity?
Answer: By generating multiple distinct mRNA isoforms from the same gene, leading to different protein variants.
23.
Why doesn’t mRNA abundance always correlate with protein abundance?
Answer: Because post-transcriptional mechanisms, such as RNA stability, translational efficiency, and protein degradation rates, heavily influence final protein levels.
24.
How can RNA secondary structures influence gene expression?
Answer: They can affect translation efficiency, localization, and interactions with RNA-binding proteins or the splicing machinery.
25.
Why is 5′ to 3′ directionality important in molecular biology?
Answer: All polymerases synthesize nucleic acids in this direction, and it establishes polarity essential for templated replication and transcription.
26.
What role does the CTD of RNA Polymerase II play in mRNA processing?
Answer: It acts as a scaffold to recruit enzymes for capping, splicing, and polyadenylation during transcription.
27.
What determines whether a gene is transcribed in a given cell?
Answer: Promoter accessibility, transcription factor binding, chromatin structure, and signaling input from the environment.
28.
What is the function of TFIIF?
Answer: It escorts RNA Polymerase II to the promoter and stabilizes the PIC.
29.
What is the function of TFIIE?
Answer: It recruits TFIIH and modulates its activity during transcription initiation.
30.
How is splicing regulated in a cell-type specific manner?
Answer: Through differential expression of splicing factors and co-factors, which can favor inclusion or skipping of specific exons in response to signals.
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Created: 2025-06-11 10:44