This family trait that skips a generation comes from an autosomal recessive trait or as Mendel called as hidden non-dominant trait. Offsprings have a dominant and recessive trait which comes from both parents. Recessive trait appears only when two offspring with same recessive trait blends. This happens in self-fertilization. In the human population, marriage is prohibited between offsprings, thus having recessive trait is only imminent when cousins are married.
The mechanism that affected the gene pool of the immigrants that entered the United states Through Ellis Island is Gene flow.
Gene flow involves the movement of genes or alleles between interbreeding populations of a particular species. In other words it is the movement of genes from one population to another population. Actually it may be an important aspect of evolution; evolution can occur as a result of genes being transferred from one population to another. Gene flow occurs when there is migration, since the loss or addition of people can easily change pool frequencies even without no other evolutionary mechanisms operating.
