Practice question

Linked genes show low frequency crossover due physical proximity on same DNA molecule, majority meioses lack exchange between them, preserving parental chromosome configurations intact. Therefore tetrads derived predominantly contain parental ditype pattern rather than tetratype or nonparental ditype patterns. As physical distance shrinks, PD approaches nearly 100 percent, TT remains low and NPD nearly zero because four-strand double crossover vanishingly rare and suppressed by interference. Diagnostic inequality PD much greater than NPD strongly suggests linkage rather than independent assortment where PD equals NPD.