Answer:
Mendel understood the disappearance of recessive traits in the first generation by conducting experiments with pea plants, and after that, creating an explanation, which we now know as the Laws of Mendel, or to be more concrete, the law of segregation.
Explanation:
In the law of segregation, it is explained that the first generation (a breed between YY and yy) always present the dominant traits of the organism, but in the second generation, since Yy organisms were being self-fertilised (this was possible since he worked with plants) he discovered that there was a possibility of recessive traits reappearing in the second generation, but only 25% percent of the offspring would have those.
An easy wat to explain this is that when you breed a homozygous dominant (YY) and a homozygous recessive (yy), you only get dominant traits, but your offspring change phenotype: you obtain 4 Yy offspring. And, when a Yy organism self-fertilises (which would be the same as breeding two Yy organisms), you get a set of 4 phenotypes: 1 YY (dominant), 1 yy (recessive) and 2 Yy (dominant), which means, 3 plants with dominant traits and 1 plant with recessive traits, and therefore the percentage, 75% dominant and 25% recessive.
Hope it helped,
BiologiaMagister
