What were the traits of the pea plants for 2 of the 5 crosses you completed?

When conducting his experiments, Mendel designated the two pure-breeding parental generations involved in a particular cross as P1 and P2, and he then denoted the progeny resulting from the crossing as the filial, or F1, generation. Although the plants of the F1 generation looked like one parent of the P generation, they were actually hybrids of two different parent plants. Upon observing the uniformity of the F1 generation, Mendel wondered whether the F1 generation could still possess the nondominant traits of the other parent in some hidden way.

To understand whether traits were hidden in the F1 generation, Mendel returned to the method of self-fertilization. Here, he created an F2 generation by letting an F1 pea plant self-fertilize (F1 x F1). This way, he knew he was crossing two plants of the exact same genotype. This technique, which involves looking at a single trait, is today called a monohybrid cross. The resulting F2 generation had seeds that were either round or wrinkled. Figure 4 shows an example of Mendel's data.

When looking at the figure, notice that for each F1 plant, the self-fertilization resulted in more round than wrinkled seeds among the F2 progeny. These results illustrate several important aspects of scientific data:

Multiple trials are necessary to see patterns in experimental data.

There is a lot of variation in the measurements of one experiment.

A large sample size, or "N," is required to make any quantitative comparisons or conclusions.

In Figure 4, the result of Experiment 1 shows that the single characteristic of seed shape was expressed in two different forms in the F2 generation: either round or wrinkled. Also, when Mendel averaged the relative proportion of round and wrinkled seeds across all F2 progeny sets, he found that round was consistently three times more frequent than wrinkled. This 3:1 proportion resulting from F1 x F1 crosses suggested there was a hidden recessive form of the trait. Mendel recognized that this recessive trait was carried down to the F2 generation from the earlier P generation.