Hello my name is Gregor Mendel welcome to my pea-plant garden I have combined a purebred yellow-seeded plant with a pure bred green -seeded plant
I only got yellow seeds! This means that the yellow coloured trait is the dominant one since it was expressed in all of the new seeds
I let the new yellow-seeded hybrid plants self-fertalise and in the second generation I got both yellow and green seeds! This meant that the green trait had been hidden by the dominant yellow. This is hidden trait is called the recessive trait.
From these results I inferred that each trait depends on a pair of factors one coming from the mother and the other from the father.
Depending on which allele was found in each seed we could have a homozygous pea where both alleles are identical. or a heterozygous pea where the two alleles are different.
We can use a punnet square to visualise how alleles are distributed amongst the descendants. By placing the different alleles on both axes and then figure out the possible combinations.
I wrote the dominant yellow allele from the pea plants as an uppercase Y and the recessive green alleles as a lowercase y. As you can see the uppercase Y overpowers the lowercase so the only time you would get green babies is if you have two lowercase y's.