Dyads are the set of two coupled chromosomes at the time of the first maturation mitosis, one of paternal origin, the other of maternal origin.
These chromatid tetrads in cell biology are characteristic features observable in prophase I of meiosis, during pachytene, during which meiotic recombinations take place.
The number of possibilities is 2^n (n is the number of dyads)
2^3 = 8 possibilities
During anaphase the is a split of dyads of maternal and paternal that can migrate independently to one of the two sides.