The experiment which he performed is testing of seed color and shape at the same time.
Explanation:
In order to see that whether the pattern of inheritance for one trait is influencing the pattern of inheritance for another Gregor Mendel worked on examining seed color and shape at the same time, and aimed his search in the color of the flower, seed shape, pod shape, seed coat tint, location of the flower, unripe color of the pod, and height of the pea plants. In order to explain the concept, the coined the terms dominant and recessive.
He used Pea plants to help him find the laws of inheritance. He crossed homozygous (AA) tall plants with short (aa) plants and found that all of the off spring were tall, due to the fact that tall is dominant and short is recessive. He then conducted another experiment where all the offspring mated (all offspring were heterozygous (Aa)) And produced the F1 generation and 25 percent of the plants were short (use a punnet square to see why) and 75 percent were tall.
I hope this response helped :) If u have anymore q about mendelian genetics pls lmk !
