*5.1.1 Autosomal dominant*

Autosomal inheritance is related to a mutation in an autosome, i.e. any chromosome that is not a sex chromosome. Dominant inheritance pattern implies that it is enough with only one mutant allele for the disease to be expressed. This means that

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*Familial Dilated Cardiomyopathy: Risk Stratification for Sudden Cardiac Death*

the effect of a mutation in a gene masks or overrides the effect of a normal variation of the same gene on the other copy of the same chromosome. Those who have only a mutation in one of their two gene copies are said to be heterozygous. Due to a complex interplay with other genes and with the environment the disease is not always expressed, this is called varying penetrance. Men and women are equally as likely to inherit a mutated gene from a parent that carries it, regardless if it is the father or mother. If one parent carries one copy of the mutated gene, the offspring has a 50% risk of inheriting it. If both parents carry one copy of the gene, the offspring has a

Autosomal recessive inheritance is caused by mutation in a gene situated on an autosome but requires both the copy inherited from the father and the copy from the mother to be mutaded. For the mutation to cause the disease to be expressed the carrier needs to be homozygous for the mutation. This inheritance pattern requires both parents to carry at least one gene affected by the mutation. Men and women are equally as likely to inherit two affected gene copies from a certain pair of parents. If both parents carry one mutated gene, the offspring has a 25% risk of

X-linked recessive inheritance pattern is caused by a mutation in a gene situated on the X chromosome. Since the X chromosome is a sex chromosome and females have two copies while males have only one copy, if the inheritance pattern is recessive, males will be affected, while females need to inherit a mutated gene from both their father and mother in order to be affected. Since men never inherit their X-chromosome from their father, the mutated gene can never pass to a son from his father. Daughters have always inherited one of their X-chromosomes from their father, thus an affected father will always have passed the mutated gene on to his daughters. This daughter will only be a carrier and not affected by the disease, unless she also has inherited the mutated gene from her mother. It is therefore common for X-linked recessive diseases to skip generations of daughters. A female that carry one mutated gene copy have a 50% risk of passing this on to both their sons and daughters.

In humans, mitochondria, and also mutations affecting mitochondrial DNA, is inherited from the mother. Both males and female can be affected by mitochondrial

In many European countries including Sweden, the physician has no legal right to contact or inform first-degree relatives about the results of a genetic test. Instead the patient must be equipped with sufficient knowledge, both verbally and in written form to inform relatives about the genetic aspect of the disease, although usually

If the proband, the first identified individual with DCM in a family, has a known disease-causing mutation it is possible to screen all first-degree relatives

disease but only females can pass on the mutation to their offspring.

*5.2.1 Family screening in case of a known mutation*

there is no legal obligation for the patient to do this.

*DOI: http://dx.doi.org/10.5772/intechopen.94437*

75% risk of inheriting at least one copy.

inheriting two mutated gene copies.

*5.1.4 Mitochondrial inheritance*

**5.2 Family screening**

*5.1.2 Autosomal recessive*

*5.1.3 X-linked recessive*

#### *Familial Dilated Cardiomyopathy: Risk Stratification for Sudden Cardiac Death DOI: http://dx.doi.org/10.5772/intechopen.94437*

the effect of a mutation in a gene masks or overrides the effect of a normal variation of the same gene on the other copy of the same chromosome. Those who have only a mutation in one of their two gene copies are said to be heterozygous. Due to a complex interplay with other genes and with the environment the disease is not always expressed, this is called varying penetrance. Men and women are equally as likely to inherit a mutated gene from a parent that carries it, regardless if it is the father or mother. If one parent carries one copy of the mutated gene, the offspring has a 50% risk of inheriting it. If both parents carry one copy of the gene, the offspring has a 75% risk of inheriting at least one copy.
