Definition. Sex-linked diseases are passed down through families through one of the X or Y chromosomes. X and Y are sex chromosomes. Dominant inheritance occurs when an abnormal gene from one parent causes disease even though the matching gene from the other parent is normal.The abnormal gene dominates.efinition. Sex-linked diseases are passed down through families through one of the X or Y chromosomes. X and Y are sex chromosomes. Dominant inheritance occurs when an abnormal gene from one parent causes disease even though the matching gene from the other parent is normal.
Savant syndrome is a rare syndrome in which people with poor mental development or brain injury possess extraordinary mental skills which are difficult to explain scientifically. Sometimes the talents of a savant may go unnoticed.he exact cause of a savant syndrome is not known. A lot of hypotheses have been proposed. Some researchers believe that there is damage to the left hemisphere of brain, which results in compensatory changes in the right side of brain.
lactose intolerance-caused by mutations in the LCT gene. At least nine LCT gene mutations cause congenital lactase deficiency, also called congenital alactasia. In this disorder, infants are unable to break down lactose (lactose intolerance) in breast milk or formula.The LCT gene mutations change single protein building blocks (amino acids) in the lactase enzyme or result in an enzyme that is abnormally short.he mutations are believed to interfere with the function of the lactase enzyme, leading to undigested lactose in the small intestine and causing severe diarrhea. Lactose intolerance in adulthood is caused by gradually decreasing activity (expression) of the LCT gene after infancy, which occurs in most humans.