Subtopic: Fundamentals of Cell structure and signaling
Question Statement:
Correctly match the following Bioinformatic tool/Database with its respective
Utility.
Bioinformatic tool/Database Utility
P. BLAST 1. Database for 3D protein structures
Q. Bowtie 2. Tool to identify similarity of a query
sequence to existing sequences available
in databanks
R. AlphaFold 3. Tool to align short read DNA sequences
obtained from Next-generation
sequencing to a reference genome
S. PDB 4. AI tool to predict protein structures
Options:
(A) P-2; Q-3; R-1; S-4
(B) P-2; Q-3; R-4; S-1
(C) P-3; Q-2; R-4; S-1
(D) P-4; Q-1; R-2; S-3
Official Answer Key:
B
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2025 Q.47)**
**1. Governing Concept**:
- **Topic**: Immunology & Major Histocompatibility Complex (MHC) Classes
- MHC molecules present peptide antigens to T lymphocytes:
- **MHC Class I**: Expressed on **virtually all nucleated cells**. Presents endogenous peptides (8–10 amino acids) derived from cytosolic proteins degraded by the proteasome to **CD8$^+$ Cytotoxic T Cells**.
- **MHC Class II**: Expressed selectively on **professional antigen-presenting cells (APCs)**: Dendritic cells, Macrophages, and B lymphocytes. Presents exogenous peptides (13–18 amino acids) derived from endocytosed antigens to **CD4$^+$ Helper T Cells**.
**2. Option Analysis**:
- **Option (A) is INCORRECT**: MHC Class I presents to CD8$^+$ T cells, not CD4$^+$.
- **Option (B) is INCORRECT**: MHC Class II is restricted to professional APCs, not all nucleated cells.
- **Option (C) is CORRECT**: Professional APCs (dendritic cells, macrophages, B cells) express MHC Class II molecules to activate naive CD4$^+$ T helper lymphocytes.
- **Option (D) is INCORRECT**: Erythrocytes are non-nucleated and lack MHC Class I entirely.
**3. Final Answer**:
- **Correct Choice**: **C**
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