Q.92. The genomes of both human and Drosophila code for an amylase that acts on the same substrate.
However, the sequence of nucleotides in the genes encoding the two is dissimilar. This is an example of
which ONE of the following types of evolution?
(A) Neutral
(B) Directional
(C) Convergent
(D) Divergent
Human and Drosophila genomes encode amylases that digest the same starch substrate, yet their nucleotide sequences differ significantly. This scenario illustrates convergent evolution, where unrelated species develop similar functions through distinct genetic paths.
Correct Answer
The correct choice is (C) Convergent. Both species independently evolved enzymes for starch breakdown due to shared dietary pressures, resulting in analogous proteins with dissimilar genes.
Option Explanations
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(A) Neutral: Refers to mutations with no fitness impact, accumulating silently without altering protein function or structure. This does not explain functional similarity from divergent sequences.
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(B) Directional: Describes selection shifting a population toward one extreme trait, like increasing body size. It applies to variation within a lineage, not cross-species functional convergence.
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**(C) Convergent: Involves distantly related species evolving similar traits independently, often for analogous functions in similar environments, producing non-homologous structures like these amylases.
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(D) Divergent: Occurs when related species from a common ancestor develop different traits, leading to homologous structures with sequence similarity, opposite to the dissimilar genes here.
