Section 4: Bioprocess Engineering and Process Biotechnology
Mass transfer in bioprocesses (kLa)
Subtopic: Fundamentals of Mass transfer in bioprocesses (kLa)
Question Statement:
’-ATGGACGTGCTTCCCgAAAGCATCGGGC-3’
R. 5’-ATGGACGTGCTTCC-AAAGCATCGGGC-3’
S. 5’-ATGGACGTGCTTCCCAAtGCATCGGGC-3’
T. 5’-ATGGACGaGCTTCCCAAAGCATCGGGC-3’
[Point mutations are shown in the lower case or ‘-’ within the sequences]
Which of the above mutant sequences DO NOT have frame-shift?
Options:
(A) miRNA
(B) siRNA
(C) shRNA
(D) snRNA
Official Answer Key:
D
Step-by-Step Solution & Explanation
### **Official Solution & Step-by-Step Derivation (GATE BT 2016 Q.15)**
**1. Governing Concept & Question Classification**:
- **Section**: BT
- **Question Type**: **MCQ** (1 Mark)
- **Topic**: Cell Biology / Cell Cycle (Phases of Eukaryotic Mitotic Division)
**2. Detailed Step-by-Step Analysis**:
- The canonical eukaryotic mitotic cell cycle proceeds sequentially through four distinct phases:
$G_1 \xrightarrow{\text{Gap 1}} S \xrightarrow{\text{DNA Synthesis}} G_2 \xrightarrow{\text{Gap 2}} M \xrightarrow{\text{Mitosis \& Cytokinesis}} G_1$
- Let us review each phase in order:
1. **$G_1$ phase**: Cell growth and preparation for DNA replication.
2. **$S$ phase**: Complete duplication of genomic nuclear DNA and centrosomes.
3. **$G_2$ phase**: Post-synthetic growth, synthesis of tubulin and mitotic machinery, and verification of DNA integrity at the $G_2/M$ checkpoint.
4. **$M$ phase (Mitosis)**: Nuclear division (prophase, metaphase, anaphase, telophase) followed immediately by cytokinesis.
- Therefore, the **$M$ phase** occurs immediately after the **$G_2$ phase**.
- **Option-by-Option Evaluation**:
- **Option (A) [INCORRECT]**: $G_0$ is a quiescent, non-dividing arrest state exited into $G_1$.
- **Option (B) [INCORRECT]**: $S$ phase is followed immediately by $G_2$ phase.
- **Option (C) [INCORRECT]**: $G_1$ phase is followed immediately by $S$ phase.
- **Option (D) [CORRECT]**: $M$ phase occurs immediately after the $G_2$ phase.
**3. Final Answer / Verification Summary**:
- **Official GATE Answer Key**: **D**
- **Scoring Criteria**: +1.0 Mark (Negative marking: -0.33 marks).
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