Among the many genetic diseases, some are sex-linked genetic diseases. The genetic rule is: a mother who carries a disease-causing gene but does not have the disease herself will only pass the disease on to a boy, while a girl is healthy (but can carry the disease-causing gene like her mother).
Such women often have men (such as brothers and uncles) in the family who are sick, while women (such as sisters and aunts) are healthy.
Hemophilia is a disease that only affects boys. With this disease, the blood does not clot easily due to the lack of a coagulation substance. Therefore, minor injuries will cause bleeding, and even without injuries, there will be subcutaneous and intra-articular bleeding. Once cerebral hemorrhage occurs, there is a fatal risk.
Experts explain that hemophilia does not mean that women will not get hemophilia, but that the proportion of men is higher. If the proportion of men in the normal population is 7%, then the proportion of women is 0.49%. Because this gene is an X-body recessive gene b, if a female has the B gene on another X chromosome, the b gene will not be expressed, while a male has only one X chromosome, so if he carries the b gene, he will definitely express it. If the mother is a patient, regardless of whether the father is normal or not, the son must be a patient; if the mother is a patient and the father is a normal person, the probability of the son being a patient is 50%; if the father is a patient and the mother is a normal person, then the daughter is a carrier; If the father is a patient and the mother is a carrier, the daughter has a 50% chance of getting the disease and a 50% chance of being a carrier; if the mother is normal and the father is a patient, the son is completely normal because the father gave the Y gene to the son. , and the gene that carries hemophilia will not be passed on to the son. This is basic genetics.
In addition, color blindness is also a genetic disease that can only be passed from mother to boy. Others include pseudohypertrophic muscular dystrophy, renal diabetes, etc., which only boys can get.
Therefore, in order to get a healthy child, it is recommended that when the male patient in the female family suffers from these diseases, it is not advisable to give birth to a boy. During pregnancy, go to the hospital for prenatal diagnosis, the male fetus will be aborted, and the female fetus will be retained.