In some plants,a purple pigment is synthesized from a colourless precursor.In a cross between two plants,one purple and the other colourless,an F₁ generation was produced that was all-purple.The F₂ produced from the F₁ had 775 purple,200 red,and 65 colourless.What is the genotype of the parents?

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The purple plant must be homozygous dominant (AABB) to produce only purple offspring. The colorless plant must be homozygous recessive (aabb) to only produce colorless offspring. The F₁ generation (all-purple) must be heterozygous (AaBb) since they are producing the purple pigment. When the F₁ generation is crossed, we can use a Punnett square to determine the potential genotypes and phenotypes of the offspring: | | AB | Ab | aB | ab | |---|----|----|----|----| | AB| AABB|AABb|AaBB|AaBb| | Ab|AABb|AAbb|AaBb|Aabb| | aB|AaBB|AaBb|aaBB|aaBb| | ab|AaBb|Aabb|aaBb|aabb| From this, we can see that 3 out of 4 potential offspring genotypes result in purple offspring (AABB, AABb, and AaBB). Therefore, the parents must have been heterozygous (AaBb × AaBb) to produce the 775 purple, 200 red, and 65 colorless offspring in the F₂ generation.

In Some Plants,a Purple Pigment Is Synthesized from a Colourless