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NEETZoologyPrinciples of Inheritance and Variation

In a cross between two pea plants, one producing large starch grains (BB) and the other producing small starch grains (bb), the F₁ heterozygotes (Bb) are observed. What will be the size of the starch grains in the F₁ generation, and which genetic phenomenon does this specific trait illustrate?

Options

  1. AIntermediate size; Incomplete dominance
  2. BLarge size; Complete dominance
  3. CBoth large and small sizes; Co-dominance
  4. DIntermediate size; Polygenic inheritance

Correct answer

A. Intermediate size; Incomplete dominance

Step-by-step solution

The gene controlling starch synthesis in pea seeds exhibits pleiotropy, as it controls both seed shape and starch grain size. For seed shape, the allele B is completely dominant over b, so Bb seeds are round. However, for starch grain size, the alleles show incomplete dominance. The BB homozygotes produce large starch grains and bb homozygotes produce small starch grains. The F₁ heterozygotes (Bb) produce starch grains of intermediate size. Therefore, the size of the starch grains in the F₁ generation is intermedia

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