In terms of the holiday model, the chromosomes can form a cruciform structure. When nicked vertically, both arms of the chromosomes contain crossover DNA (see part f of diagram).
However, it is stated as a principle of human genetics that
"When a chiasma forms between two gene loci, only half of the mitotic products will be of crossover type".
Yet in this case all of the mitotic products will be of crossover type when vertical nicking occurs. How can the Holiday model be reconciled with the above statement? It doesn't make sense to me. Is it because the holiday model does not represent what naturally occurs in the human body?