For instance, seeds of white flowered plants produce plants with white flowers as well.
Some plants do cross-fertilize in nature.
Mendel tracked the observable traits to determine if there were certain patterns of inheritance. Because Mendel was a mathematician, he used probability theory to predict the possible outcomes of a cross. This is shown by using Punnet squares. Huntington's disease Occurs in 1 out of 20,000 births neurodegenerative disorder leading to severe muscle spasms and personality disorders, usually not apparent until middle age. Affected individuals lack the enzyme needed to breakdown the amino acid phenylalanine.