Practice question

Probability of crossover between two markers during prophase I rises with physical separation because longer DNA stretch offers more opportunity for chiasma formation and exchange between homologous chromatids. Over short distances recombination frequency approximates linear function of base pair distance enabling use as mapping ruler for gene ordering. Adjacent genes show near zero recombination, distant genes approach fifty percent ceiling of independent assortment. Chromosome length alone insufficient, specific inter-marker interval length determines frequency modulated by interference and hotspot distribution explaining variation along chromosome arms.