The first generation: 1 is XAY, and there is only one band in the electrophoresis map, which is A; Number 2 has two belts, a and a;

So the genotype of the first generation is XAY of 1 and XAXa of 2.

In the second generation, 1 has a band, but this band is different from the first generation, so the second generation 1 contains a gene;

Because the first generation 1 has no gene, but the offspring appear recessive homozygote, so the genotype of the second generation 1 is XaY, which means that the disease is recessive with X.