When judging biological genetic diseases, there is a formula to understand: out of nothing, it is recessive, recessive inheritance looks at female diseases, and father and son are sick partners; create/beget/fabricate (sth) out of nothing

The first step: judging whether it is a dominant genetic disease or a recessive genetic disease: out of nothing, out of nothing, and both normal parents have had sick children, which belongs to a recessive genetic disease. There is nothing dominant in middle school, but if both sick parents give birth to normal children, the disease is a dominant genetic disease. .

Step 2: judge whether it is autosomal inheritance or X inheritance. Through the last two sentences of each formula, it can be judged whether it is autosomal or X-chromosome genetic disease.

In the recessive inheritance with X, the mother is sick, and both X chromosomes carry recessive pathogenic genes, so there must be a recessive pathogenic gene passed on to her son along with one X chromosome (genotype is XY), and there is no equivalent gene on her son's Y chromosome, so a recessive pathogenic gene makes men sick. Similarly, when a daughter is sick, both X chromosomes carry recessive pathogenic genes, and there must be a recessive pathogenic gene inherited from her father along with one X chromosome (genotype XY). Generally speaking, in a family with X recessive inheritance, a woman has X recessive inheritance, and her father and son should be patients. If the father or son of a female recessive genetic disease is not sick, it is autosomal recessive inheritance.

In inheritance with X dominance, the same is true. In a family with X-dominance, a man suffers from X-dominance genetic disease, and both his mother and daughter should be patients.

If a man suffers from a dominant genetic disease in a dominant genetic family, then whether his mother and his daughter are patients can be judged as autosomal dominant inheritance.