Q.Hugo de Vries first used the term mutation based on his observation on :

Insertion or deletion of one or more base pairs shifts the reading frame of the genetic code from that point onward, so it is called a frameshift mutation.

Since the genetic code is read in triplets (codons) starting from a fixed point, inserting or deleting a number of bases that is NOT a multiple of three shifts the entire downstream reading frame, changing eve …

Adding or removing base pairs (not in multiples of three) shifts the reading frame of the genetic code downstream of the mutation.

The genetic code is read from a fixed starting point in triplets (codons). If one or two base pairs are inserted or deleted in the DNA (not a multiple of three), every codon downstream of that point is displaced/shifted, changing the entire amino acid sequence translated from that point onward. …

A point mutation involves a change at just one nucleotide/base-pair position in DNA, which can alter the codon and hence the amino acid encoded at that position in the protein.

Mutations are permanent, heritable changes in the sequence of DNA (or chromosomes). When such a change is restricted to a single base pair - substitution of one nucleotide for another, or occasionally insertion/deletion of a single base - it is called a point mutation.

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Point mutation = alteration of just one nucleotide/base pair in the DNA sequence.

A point mutation is the simplest type of gene mutation, arising from a change at a single point (base pair) in the DNA sequence. It commonly occurs through substitution of one base pair for another. A classic example is sickle-cell anaemia in humans, caused by a single base substitution (GAG → GTG) in the sixth codon of the β-globin gene, changing the amino acid glutamic acid to valine, which alters the shape and function of haemogl …

De Vries's Mutation Theory (1901) was based on Oenothera lamarckiana.

Hugo de Vries, studying populations of the evening primrose Oenothera lamarckiana growing wild near Amsterdam, observed several distinct, novel heritable variant forms appearing abruptly among normal plants. Interpreting these sudden, discrete hereditary changes as a new source of variation (distinct from ordinary continuous variation), he coined the term 'mutation' in his Mutation Theory (1901), proposing that such abrupt heritable changes could be a mechanism for the origin of new species. (It was later shown …