Mutation Theory
திடீர் மாற்றக் கொள்கை
Darwin spoke of gradualism, but nature often leaps. Hugo deVries proved that evolution isn't always a slow crawl; it is a sudden, violent shift in the genetic code. Do not confuse minor variations with the raw power of mutation.
The idea
Hugo deVries proposed the Mutation Theory based on his work on Oenothera lamarckiana. He defined evolution as a saltatory process, meaning it occurs through large, random, and directionless mutations. Unlike Darwinian variations which are small and directional, these mutations are sudden and heritable. This theory fundamentally challenges the concept of gradual accumulation of traits.
Why it matters
It explains the sudden appearance of new phenotypes that cannot be accounted for by slow, incremental changes alone.
NEET lens
NEET focuses on the term 'Saltation'—memorize it as 'single step large mutation'. Distinguish clearly between Darwin’s 'minor variations' and deVries’ 'mutations'. Questions often test the difference between directional evolution and random, directionless mutation.
Clinical significance
In humans, uncontrolled mutations lead to oncogenesis. When DNA repair mechanisms fail, somatic mutations accumulate, transforming normal cells into malignant tumors. This is the lethal side of the same mechanism that drives evolutionary change.
Introduction
Hugo de Vries, working on the evening primrose (Oenothera lamarckiana), proposed that evolution is caused by mutation — large, sudden variations — rather than by the small variations Darwin emphasised.
Core concept
De Vries' ideas: mutations are large difference arising suddenly in a population; mutations are random and directionless, whereas Darwinian variations are small and directional; it is mutation that causes speciation — he called it saltation (a single-step large mutation). Darwin's evolution is gradual; de Vries' is saltatory. Today, mutation is recognised as the ultimate source of genetic variation, acted upon by natural selection.
Go deeper
Both views are now combined: mutations provide new variation, and natural selection, drift and other factors shape how common those variations become.
From Class 10
Sometimes a plant suddenly appears very different from its parents because of a change in its genes — that sudden jump is what de Vries called mutation.