<Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (October 2013) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (October 2013) (Learn how and when to remove this template message) </Td> </Tr> <P> A hereditary carrier (or just carrier), is a person or other organism that has inherited a recessive allele for a genetic trait or mutation but does not display that trait or show symptoms of the disease . Carriers are, however, able to pass the allele onto their offspring, who may then express the genetic if they inherit the recessive allele from both parents . The chance of two carriers having a child with the disease is 25% . This phenomenon is a direct result of the recessive nature of many genes . </P> <P> Queen Victoria, and her daughters Princesses Alice and Beatrix, were carriers of the X-linked hemophilia gene (an abnormal allele of a gene, necessary to produce one of the blood clotting factors). Both had children who continued to pass on the gene to succeeding generations of the royal houses of Spain and Russia, into which they married . Since males only have one X chromosome, males who carried the altered gene had hemophilia . Females have two X chromosomes, so one copy of an X-linked recessive gene would cause them to be an asymptomatic carrier . These females simply passed it to half of their children . </P>

When might it be important to know if one is a carrier