Probability represents the odds that a certain situation will happen. It can be calculated.

The law of independent assortment explains that gamete cell inherits alleles for various genes separately of one another. Therefore, the offspring inherits two alleles, one from each parent, that determine its appearance. In the example of height, the dominant allele determines the tallness, while the recessive allele determines shortness. When a plant inherits one, or two dominant alleles from its parents, that will define the tallness. The shortness of the offspring will appear only if the recessive allele is inherited from both of the parental plants. If the genotype of the parental plants is Tt and Tt are several possibilities for the genotype of an offspring – TT, Tt, Tt, and tt. In this experiment, Mendel concluded that even two tall plants can give a short offspring because there are 25% odds for the plant to inherit genotype tt.

Mendel’s contribution to genetics is great because he was the first one to explain and prove the basic principles of heritage. He had discovered that biological inheritance is determined by genes, which are passed from one generation to the offspring. The segregation law explains the process that occurs in the parental generation, where gametes contain only one, randomly chosen allele. Mendel also concluded that alleles for different traits can be dominant or recessive. In order for the dominant trait to appear, only one dominant allele must be present, while the genotype must contain two recessive alleles for the recessive characteristic to occur in the phenotype.

Homozygous genotype is present when an offspring inherits the same alleles (both dominant or both recessive), while heterozygous genotype means that one recessive and one dominant allele are inherited. Homozygous dominant genotype in this specific example is YY, homozygous recessive is yy, while heterozygous is Yy. The dominant allele determines the yellow, while the recessive allele determines green color. When a plant inherits one (Yy), or two (YY) dominant alleles from its parents, that will define the yellow color. The appearance of the offspring will be green only if the recessive allele is inherited from both of the parental plants – genotype yy.

The woman is homozygous dominant and has the genotype HH, while the man is homozygous recessive which is hh. The disease will manifest in their child only if it inherits both recessive alleles, which is impossible. If the child has only one dominant allele, it will be healthy, but it can pass on the recessive allele to their own offspring. The Punnett square, where the parental gametes are blue colored, will look like this:
begin{center}
begin{tabular}{ c c c}
& {color{Blue}h} & {color{Blue}h}\
{color{Blue}H} & Hh & Hh\
{color{Blue}H} & Hh & Hh
end{tabular}
end{center}