The two examples that come readily to mind are the Hardy-Weinberg law that applies to ratios of genes in a population under particular conditions and the law of independent assortment
of chromosomes applied to the partitioning of chromosomes during meiosis.
Mendel's laws of segregation and the law of independent assortment
of characters are now recognized as the fundamental principles of heredity.
The inheritance of one element does not govern the inheritance of any other element; this is the law of independent assortment.
This is his law of independent assortment. He was able to prove his two laws because he (1) carefully selected his experimental subjects for a limited number of traits and (2) had a large population, which allowed him to treat the result statistically.
One of the processes that ultimately provides for new combinations of alleles in sexually-reproducing organisms is the independent assortment
of chromosomes during meiosis 1.