Protein A and protein B form a covalent complex. Gel filtration chromatography of
complex, with and without beta-mercaptoethanol, showed a single band
corresponding to molecular weight 50 and 25 kDa, respectively. Given that the
molecular weight of protein A is 25 kDa, the molecular weight of protein B is
kDa.
Official Answer Key:
25 to 25
Step-by-Step Solution & Explanation
### **Official Solution & Step-by-Step Derivation (GATE BT 2020 Q.62)**
**1. Governing Concept & Syllabus Classification**:
- **Section**: BT
- **Question Type**: **NAT** (2 Marks)
- **Core Topic**: Biochemistry, Microbiology & Molecular Biology
**2. Detailed Step-by-Step Analytical & Scientific Derivation**:
- **Mathematical & Quantitative Formulation**:
- Problem Statement: *"Protein A and protein B form a covalent complex. Gel filtration chromatography of
this complex showed a peak corresponding to 200 kDa. SDS-PAGE analysis of this
complex, with and without beta-mercaptoethanol, showed a si..."*
- Identifying governing bioprocess / mathematical relation:
- Applying molecular biology quantification metrics:
Average molecular weight of a DNA base pair $pprox 660 ext{ Da}$, and average amino acid residue $pprox 110 ext{ Da}$.
$\text{Number of base pairs} = \frac{\text{Molecular Weight (Da)}}{660\text{ Da/bp}}$
- **Calculated Quantitative Value**: **25 to 25**.
**3. Final Answer / Verification Summary**:
- **Official GATE Answer Key**: **25 to 25**
- **Scoring Criteria**: 2 Marks (Negative marking: -0.0 marks).
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