Q.47 An estimate of phylogenetic relationships among the taxa is commonly represented in the form of a
(A) Cladogram (B) Idiogram (C) Phenogram (D) Dendrogram
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Phylogenetic Relationships Cladogram
In evolutionary biology and bioinformatics, understanding phylogenetic relationships cladogram is essential for mapping how species or taxa evolved from common ancestors. Question 47 from competitive exams like NEET, CSIR UGC NET, or GATE Biotechnology asks: “An estimate of phylogenetic relationships among the taxa is commonly represented in the form of a (A) Cladogram (B) Idiogram (C) Phenogram (D) Dendrogram.”
This MCQ tests your grasp of tree-like diagrams in molecular biology and genetics. Let’s break it down with the correct answer and clear explanations of all options.
Correct Answer: (A) Cladogram
A cladogram is the standard tool for depicting phylogenetic relationships cladogram among taxa. It shows evolutionary branching patterns based on shared derived characteristics (synapomorphies), ignoring overall similarity or time.
Cladograms use a tree structure where nodes represent common ancestors and branches indicate divergence. They’re widely used in cladistics, a method popularized by Willi Hennig, and form the backbone of modern phylogenetics in tools like BLAST or CLUSTAL for sequence alignment.
Why cladogram? Unlike other diagrams, it focuses purely on ancestry and cladistic relationships, making it the go-to for estimating evolutionary history.
Detailed Explanation of All Options
Cladogram (Correct Choice)
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Represents phylogenetic relationships as a hypothesis of evolutionary relatedness.
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Based on shared traits; no branch lengths (time or distance not implied).
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Example: In human-chimp-gorilla phylogeny, it shows branching from a common ancestor.
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Common in: Bioinformatics pipelines for gene trees.
Idiogram (Option B)
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A diagrammatic representation of chromosomes in a genome, arranged by size and shape.
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Used in cytogenetics to show banding patterns (e.g., G-banding).
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Not for phylogeny—focuses on karyotype analysis, like in genetic disorders or species identification.
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Example: Human idiogram displays 46 chromosomes with centromere positions.
Phenogram (Option C)
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Clusters taxa based on overall phenotypic similarity (observable traits).
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Uses distance-based methods (e.g., UPGMA algorithm), assuming equal evolutionary rates.
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Doesn’t strictly reflect phylogeny; can group convergent evolution artifacts.
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Example: Plants with similar leaf shapes might cluster despite distant ancestry.
Dendrogram (Option D)
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A general tree diagram from hierarchical clustering, used in various fields.
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In phylogenetics, it may show relationships but often includes branch lengths for genetic distance.
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Broader term—not specific to cladistic phylogeny; common in microbiology for strain typing.
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Example: Dendrograms from PCR-RFLP data in microbial diversity studies.
| Option | Primary Use | Basis of Grouping | Phylogenetic Focus? |
|---|---|---|---|
| Cladogram | Evolutionary ancestry | Shared derived traits | Yes (pure) |
| Idiogram | Chromosome mapping | Size, shape, bands | No |
| Phenogram | Phenotypic similarity | Overall trait distance | Partial |
| Dendrogram | Hierarchical clustering | Distance metrics | Variable |
Why This Matters for Exams and Research
Mastering phylogenetic relationships cladogram helps in topics like molecular evolution, microbial phylogeny, and bioengineering. For bioinformatics enthusiasts, tools like MEGA or PhyML generate cladograms from DNA sequences.
Practice similar MCQs to ace your exams—cladograms appear frequently in questions on tree-building algorithms.
