Why is it important for Mendel's pea plant to be a purebred variety?

Note: Y = Yellow Gene, R = Round Gene, G = Green Gene, W = Wrinkle Gene. Any combination in an "equation" refers to a plant with those genes; there will be four letters because Mendel used pure breeds in his pea-plant experiments that carried only genes that were yellow and round together, and only genes that were green and wrinkled together. Peas have two of each gene type in his examples. Y and G affect colors, while R and W affect shape.

(SKIP THE NEXT TWO PARAGRAPHS IF YOU ALREADY UNDERSTAND WHAT MENDEL DID.)

He was able to conclude that genes were passed down from parents to their offspring as a result of these experiments because when plants crossed with a plant that had the same characteristics, the offspring had the same characteristics (e.g. YYRR + YYRR -> YYRR and GGWW + GGWW -> GGWW).

After determining which parent would pass traits by testing YYRR + GGWW, he produced a plant that appeared to be YYRR; however, when that plant was bred with another GGWW, it produced an offspring that was GGWW. This didn't make sense until he looked into it more and found that the first offspring, which looked to be YYRR, was actually YGRW. This led him to the conclusion that plants with dominant genes that show can still have recessive traits within that can still be passed on.

If he wasn't guaranteed pure breeds in his pea plants, he might have had several pea plants with genetic makeups similar to the YGRW example, without realizing it contained hidden traits. If these kinds of plants were the originals, and he carried out the experiments in the manner he did, every outcome would differ rather than the consistent results he obtained from the first round, as he actually did.

Much of what we know about the functions of life may not have found its way into the scientific community as much of what we know today is based on the knowledge Mendel shared. Overall, if the impure breeds had led the experiment, it would have set science as we know it much further back in terms of medication.

For Mendel's experiments, using purebred varieties of pea plants was crucial because it ensured that each plant would consistently pass on specific genetic traits to their offspring. This predictability allowed Mendel to accurately trace the inheritance patterns of particular traits (such as flower color or seed shape) across generations. Purebred plants, having homozygous alleles for a trait, eliminated variability in trait expression due to genetic background, making it possible to observe and deduce the principles of genetic inheritance, including dominant and recessive traits, segregation, and independent assortment.