 At the end of the last Ice Age, 10,000 years ago, our hunter-gatherer ancestors began keeping flocks and herds and cultivating crops. Farmers began to selectively breed certain traits into and out of their animals and plants. This has been happening for thousands of years, but the knowledge of the actual genetics behind it was relatively unknown until the last 100 years or so. We have all heard of Charles Darwin, right? It was actually the lesser known scientist turned monk, Gregor Mendel, that came up with the correct hypothesis for how inheritance of traits work, whereas Darwin, Lamar and other leading scientists had failed. Mendel published his ideas in 1866, but it took until the 1900s for his ideas to be recognized. Mendel studied the inheritance of different characteristics in pea plants. He found that when he bred purple flowered plants with white flowered plants, the offspring would either be white or purple. Not a mixture of the two, or pale purple. He also noticed that. This held true for other traits, like the seed and the podcaller, either being yellow or green, and not a mix. And the stems being long or short, and not somewhere in the middle, Mendel concluded that inheritance of characteristics is determined by units that are passed from parents to offspring unchanged. You either inherit your mother's genes, or your father's genes, and not a mixture. When looking at the green or yellow pea pods, Mendel found that the first generation offspring from a yellow pod and a green pod parent will have a yellow pea pod. But the second generation will have green pods in a 3 to 1 ratio. This led to Mendel proposing that a trait might not show up in an individual, but can still be passed on to the next generation. Mendel had discovered dominant and recessive genes. Watch our video on common terms used in genetics, if you are unsure about dominant and recessive genes and genes in alias. The gene for yellow pods is dominant, and the green pod gene is recessive. Notice how we have the parent generation, and then the first generation is called F1, and the second generation is called F2. Genetic diagrams are great for showing how this works. We have two parents. The yellow pod parent with the two dominant yellow genes, notice how their dominant traits are given a capital letter, and the green pod parent with the two recessive green genes, which are shown by a smaller letter. These are the possible gametes, and these are the possible genotypes of the offspring. Because the yellow gene is dominant, all of the offspring will have the yellow pod phenotype, but do carry the green recessive gene. Now let's see what happens if we cross two of the F1 offspring generation. And in our next generation, F2, we have three yellow pods, but this time we have a green pod offspring that has both recessive green genes. Mendel consistently found this three to one ratio in later generations as well, which led him to his proposal that traits might not show up in an individual, but can still be passed on to the next generation. You can be a carrier of a gene that codes for a different phenotype, but not actually show the phenotype yourself. Remember that the phenotype is just what is physically expressed as the green pod color. We can also show this information in a punnard square. We will look at punnard squares in more detail in our punnard square video. So from this video, you should now know that through observing the phenotypes of lots of crosses of pea plants, George Mendel proposed that you either inherit a gene from your mother or from your father, and not a mixture of both. And because of recessive genes, traits may not show up in an individual, but can still be passed on to the next generation, it may show up there instead. As with the green pods.