So we have this pun and square right over here. So we produce X, uppercase BX, lowercase BX. This should be XY x lowercase by x uppercase B, x lowercase BX, lowercase B and Y. So notice what we see. We see that if we produce a female, both females must be heterozygous. But if we produce a male, the male must express the phenotype for that disease because in both cases, they have the lowercase B.