AVP cannot bind with it, and NDI results. The V2R gene is carried on the X chromosome . The X chromosome is known as the female sex chromosome, as females have two, and males have only one. Females, then, have a V2R gene on each of their X chromosomes, so they have a pair of V2R genes. If one of those V2R genes is mutated, they have another V2R gene on their other X chromosome that may not be mutated.
Males only have one X chromosome, which they inherit from their mother.
The sons, in turn, will pass on the gene to all of their daughters and none of their sons. Females who carry the mutated V2R gene can express the symptoms of NDI to varying degrees but rarely as severely as do their sons. The reason they can express lighter symptoms is because the normal V2R gene may not be able to completely compensate for the mutated one. All of a female's X chromosomes in the cells in excess of one are inactivated by some unknown process called X-inactivation . In some cells, the X chromosome with the NDI gene is inactivated.