Purple

Dr. Foster: ‘That’s correct! Based on your findings, purple is the dominant phenotype because it shows up in the majority of the offspring. Even though Mendel saw all purple flowers among the F1 generation, he still needed to figure out whether those purple plants were homozygous or heterozygous.’

You: ‘So if all F1 flowers are purple, they could be AA or Aa, right? Mendel wouldn’t automatically know just by looking at them?”

Dr. Foster: ‘Exactly. That’s why he designed experiments using Punnett squares as a predictive tool. He already understood that the white pea flower was homozygous recessive, or ‘aa.’ The purple parent might have been homozygous dominant (AA) or heterozygous (Aa).’

[Another student pulls over a tablet for a demonstration.]

Alice: ‘I’ll quickly set up the Punnett square here—just like Mendel would—to explore the possible genotypes. Then we can see how each combination leads to specific offspring ratios.’

Dr. Foster: ‘Great idea. This is how Mendel laid the groundwork for understanding inheritance patterns. Let’s work through that square step by step.’

Pick the correct illustration of Punnett square!

Punnett square 1:

Punnett square 2: