Here's why:
* True-breeding organisms: These organisms are homozygous for a particular trait, meaning they have two identical alleles for that trait.
* Crossbreeding: When two true-breeding organisms with contrasting traits are crossed, their offspring (F1 generation) inherit one allele from each parent.
* Dominant and recessive alleles: Some alleles are dominant, meaning they mask the expression of the other allele (recessive allele).
* F1 generation: Since one parent carries the dominant allele, the F1 generation will express the dominant trait, even if they carry the recessive allele.
* Recessive trait: The trait associated with the recessive allele is only expressed when an organism inherits two copies of the recessive allele (homozygous recessive). This happens in the F2 generation when the F1 generation self-pollinates or interbreeds.
Example:
* Let's say one true-breeding parent has purple flowers (PP, dominant allele for purple) and another has white flowers (pp, recessive allele for white).
* Their F1 generation will all have purple flowers (Pp) because they inherit one dominant allele from the purple-flowered parent and one recessive allele from the white-flowered parent.
* However, the recessive allele for white flowers is still present in the F1 generation. When the F1 generation self-pollinates, some of the offspring (F2 generation) will inherit two copies of the recessive allele (pp) and will express the white flower trait.
