Question

While working on Oenothera lamarckiana or evening primrose, Hugo de Vries observed

• A. that all offspring produced by this plant after selfing were of the same type
• B. that the majority of offspring produced by this plant were similar to the parental type but few seemed different
• C. that on selfing the mutants, all offspring produced resembled the parents
• D. all of these

Answer 1

The correct option is B that the majority of offspring produced by this plant were similar to the parental type but few seemed different

The term mutation was coined by Hugo de Vries. He believed that single step large mutations (saltations) are responsible for the appearance of new variants that form entirely new species in a single generation. He worked on Oenothera lamarckiana or evening primrose and proposed the mutation theory of evolution.

The evening primrose plants undergo self-pollination.
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On selfing it was observed that the majority of the offspring were similar to the parental type, however, few offspring were phenotypically different from others. These differences are due to mutation and these organisms are called mutants.
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On further selfing of the mutant plant, he observed that the majority of the offspring resembled the mutant parent, however, there were again few plants phenotypically different from the parent.

He observed that the number of chromosomes changed with change in the variety of plants. The mutants could pass on the mutations to subsequent generations without blending. Therefore, he was convinced that evolution takes place by sudden large inheritable changes in the genetic makeup of the organism. He called these large mutations as saltations.