X-Linked Recessive Inheritance
X-linked means the gene is located on the X chromosome, one of two sex chromosomes. Genes, like chromosomes, usually come in pairs. Recessive means that when there are two copies of the responsible gene, both copies must have a disease-causing change (pathogenic variant) in order for a person to have the disease. Mutation is an older term that is still sometimes used to mean pathogenic variant.
Because women have two X chromosomes, a pathogenic variant for an X-lined recessive disease generally needs to occur in both copies of the gene to cause the disease. Because men have one X chromosome and thus only one copy of the gene, a pathogenic variant in their one copy is enough to cause the disease. Women who have a pathogenic variant in one copy of the gene, are called carriers. In rare cases, women carriers may experience mild to moderate symptoms but most have no symptoms.
A woman who carries one X-linked gene variant has a 50% (1 in 2) chance of having a son with the disease and a 50% (1 in 2) chance of having a daughter who is a carrier. A man with an X-linked recessive disease cannot pass on the disease to his sons, but all of his daughters will be carriers. If a male child is the first person in a family with the disease, the pathogenic variant may have been inherited from the mother or may have occurred by chance for the first time in the child (de novo).X-linked means the gene is located on the X chromosome, one of two sex chromosomes. Genes, like chromosomes, usually come in pairs. Recessive means that when there are two copies of the responsible gene, both copies must have a disease-causing change (pathogenic variant) in order for a person to have the disease. Mutation is an older term that is still sometimes used to mean pathogenic variant.
Because women have two X chromosomes, a pathogenic variant for an X-lined recessive disease generally needs to occur in both copies of the gene to cause the disease. Because men have one X chromosome and thus only one copy of the gene, a pathogenic variant in their one copy is enough to cause the disease. Women who have a pathogenic variant in one copy of the gene, are called carriers. In rare cases, women carriers may experience mild to moderate symptoms but most have no symptoms.
A woman who carries one X-linked gene variant has a 50% (1 in 2) chance of having a son with the disease and a 50% (1 in 2) chance of having a daughter who is a carrier. A man with an X-linked recessive disease cannot pass on the disease to his sons, but all of his daughters will be carriers. If a male child is the first person in a family with the disease, the pathogenic variant may have been inherited from the mother or may have occurred by chance for the first time in the child (de novo).
Because women have two X chromosomes, a pathogenic variant for an X-lined recessive disease generally needs to occur in both copies of the gene to cause the disease. Because men have one X chromosome and thus only one copy of the gene, a pathogenic variant in their one copy is enough to cause the disease. Women who have a pathogenic variant in one copy of the gene, are called carriers. In rare cases, women carriers may experience mild to moderate symptoms but most have no symptoms.
A woman who carries one X-linked gene variant has a 50% (1 in 2) chance of having a son with the disease and a 50% (1 in 2) chance of having a daughter who is a carrier. A man with an X-linked recessive disease cannot pass on the disease to his sons, but all of his daughters will be carriers. If a male child is the first person in a family with the disease, the pathogenic variant may have been inherited from the mother or may have occurred by chance for the first time in the child (de novo).X-linked means the gene is located on the X chromosome, one of two sex chromosomes. Genes, like chromosomes, usually come in pairs. Recessive means that when there are two copies of the responsible gene, both copies must have a disease-causing change (pathogenic variant) in order for a person to have the disease. Mutation is an older term that is still sometimes used to mean pathogenic variant.
Because women have two X chromosomes, a pathogenic variant for an X-lined recessive disease generally needs to occur in both copies of the gene to cause the disease. Because men have one X chromosome and thus only one copy of the gene, a pathogenic variant in their one copy is enough to cause the disease. Women who have a pathogenic variant in one copy of the gene, are called carriers. In rare cases, women carriers may experience mild to moderate symptoms but most have no symptoms.
A woman who carries one X-linked gene variant has a 50% (1 in 2) chance of having a son with the disease and a 50% (1 in 2) chance of having a daughter who is a carrier. A man with an X-linked recessive disease cannot pass on the disease to his sons, but all of his daughters will be carriers. If a male child is the first person in a family with the disease, the pathogenic variant may have been inherited from the mother or may have occurred by chance for the first time in the child (de novo).
