As with some of the other conditions we have mentioned, this one seems to affect particular groups more than others. As all the cells divide during growth and development, cells that arise from the cell with the altered gene will have the mutation, while other cells will not. Once known as a harelip, the cleft palate was said to have formed as a result of the mother's being frightened by a hare while she was carrying the child. Likewise, goldfish, yellow roses, and Concord grapes are all descendants of ancestors with specific mutations. This is an example of a hereditary mutation. In other cases, the mutation occurs in the fertilized egg shortly after the egg and sperm cells unite. C D ISORDERS In the past, all manner of superstitions arose to explain why a child was born, for instance, with a cleft palate, a situation in which the two sides of the roof of the mouth fail to meet, causing a speech disorder that may be mild or severe. Whereas the worldwide incidence of this rare condition is about one in one million, among Libyan Jews the rate is higher. It produces shaking and a range of other symptoms, including depression, irritability, and apathy, and is usually fatal. If this DNA has a mutation, the child that grows from the fertilized egg will have the mutation in each of his or her cells. It also has resulted in crops that are resistant to drought or insects or which have a high yield per acre. Depending on the mutation and how many cells are affected, mosaicism may or may not cause health problems. Genetic alterations that occur in more than 1 percent of the population are called polymorphisms. Most disease-causing gene mutations are uncommon in the general population. The red individual has inherited two mutated alleles of a gene from their parents.