Section 3: Genetics, Cellular and Molecular Biology
Recombinant DNA technology
Subtopic: Fundamentals of Recombinant DNA technology
Question Statement:
The maximum parsimony method is used to construct a phylogenetic tree for a
set of sequences. Which one of the following statements about the method is
CORRECT?
Options:
(A) Nuclease, DNA polymerase, DNA ligase
(B) Nuclease, DNA ligase, helicase
(C) Primase, DNA polymerase, DNA ligase
(D) Primase, helicase, DNA polymerase
Official Answer Key:
A
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2022 Q.44)**
**1. Governing Concept**:
- **Topic**: Bioinformatics & Molecular Phylogenetics (Maximum Parsimony)
- The **Maximum Parsimony (MP)** method is a character-based phylogenetic reconstruction algorithm based on Occam's razor principle.
- It evaluates all possible unrooted tree topologies and selects the optimal phylogenetic tree that **minimizes the total number of evolutionary changes (substitutions/mutations)** required to explain the observed sequence variations across all informative sites.
**2. Option Analysis**:
- **Option (A) [minimizes the steps required to generate the observed variations] is CORRECT**: Defining criterion of maximum parsimony.
- **Option (B) is INCORRECT**: Maximizing changes contradicts parsimony.
- **Option (C) is INCORRECT**: Branch point count is topologically fixed for a bifurcating tree of $n$ taxa ($n-2$ internal nodes).
- **Option (D) is INCORRECT**: Maximum Likelihood and Bayesian methods employ explicit statistical probability calculations, not parsimony.
**3. Final Answer**:
- **Correct Choice**: **A**
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