So once again, this can arise as a result of nondisjunction. But now let's study nondisjunction as it takes place in the male individual. So in this case, we begin by assuming we have a normal female individual. Now, we're going to assume we have a normal male individual and that means we have one X and we have one Y. Now, during interface we have replication taking place and so we produce this identical cystochromatid with respect to this one and this identical system chromatid with respect to this one. And if we fast forward to metaphase one of meiosis, we basically get these chromosomes line up the tetramer of chromosomes lineup at the equatorial plate.