Question

What discoveries in genetics have led to the realization that genetic mapping is not quite as simple as genes being linked or not? List two in your answer and explain how they added layers to our current understanding of mapping and gene expression. An example is epigenetics, the field of genetics that tracks expression based on environmental factors. Someone might carry two closely associated ("linked") genes, but one's expression is modified by environmental factors, making interpretation of whether they (genes) behave according to Mendelian principles difficult. Provide two more examples and list why you think they have made studying gene linkage somewhat tricky.