Many specific diseases are known (see. Examples of Generkrankungen in Mendelian inheritance).
caused by a single gene genetic disorders (Mendelian disorders) are to be examined most easily and are best understood. When expression of a characteristic (an allele) requires only one copy of a gene, this feature is dominant. When expression of a feature requires 2 copies of a gene (alleles 2), this characteristic is recessive. An exception are the X-linked diseases. Since men have not paired allele usually to compensate for the effects of most alleles on the X chromosome, the X chromosome allele is expressed in men, even if the feature is recessive. Other exceptions, such as mitochondrial diseases, is also available. Mitochondrial genes are usually inherited only from the mother’s egg. Many specific diseases are known (see. Examples of Generkrankungen in Mendelian inheritance). Examples of Generkrankungen in Mendelian inheritance gene Dominant Recessive non-X-linked Marfan syndrome Huntington’s disease Cystic fibrosis X-linked hereditary rickets hereditary nephritis red-green color blindness Hemophilia autosomal dominant inheritance to occurrence of an autosomal dom inant inherited feature only one allele of a gene is necessary; d. H. It affects both heterozygotes and homozygotes than the altered gene. A typical pedigree for an autosomal dominant inherited feature is shown in (autosomal dominant inheritance.). Generally, the following rules apply: A person concerned has an affected parent. If the affected parent is heterozygous and the other is not affected, they will have on average the same number of affected and non-affected children; d. H. each child of an affected person carries a 50% risk that the feature also occurs in him. Not Diseased children of affected parent does not give the characteristic to their offspring. Men and women are affected equally high probability. Autosomal dominant inheritance. Autosomal recessive inheritance Thus a autosomal recessive trait interspersed, two copies of a variant allele must be present. An exemplary pedigree is autosomal recessive inheritance. shown. Generally, the following inheritance rules apply: If normal parents have an affected child, both parents are heterozygous. On average, a quarter of their children are affected, half are heterozygous, and a quarter are normal. Therefore, the probability that a child’s disorder is not inherited in three quarters, and the probability of an unaffected child is a carrier of the gene in two thirds. All children of an affected parent and genotypically normal are phenotypically normal and heterozygous. Of the children of an affected parent and a heterozygous half are disproportionately affected and heterozygous half. If both parents are affected, and all their children are concerned. Men and women are affected equally high probability. Heterozygous are phenotypically normal, but carriers of the trait. Autosomal recessive inheritance. Since relatives are more likely to have the same mutated allele closely related pairs (blood relatives) get more likely affected children. In parent-child or brother-sister compounds (incest), the risk of having sick children, especially high because a high proportion of their genetic material matches. In certain populations, the proportion of heterozygotes (carriers) may be particularly high because a “founder effect” has been felt (ie below the initially few group members there was a carrier) or because the carrier state meant a selective advantage (heterozygous for sickle cell anemia, for protecting . B. from malaria). Due the feature a specific protein defect, the protein of interest (eg., An enzyme) is usually heterozygotes in lesser concentration. If the mutation is known heterozygous phenotypically normal people using molecular genetic techniques can be identified (eg. As in most cases in people with cystic fibrosis). X-chromosomal dominant inheritance X-linked dominant inherited traits are transferred with the X-chromosome; most only rarely. Normally, men are more affected, some X-linked dominant diseases are often fatal to them. Women who carry only one abnormal allele are affected, but less strongly. A typical family tree can be seen in X-linked dominant inheritance. X-linked dominant inheritance In general, make the following rules of inheritance: Affected males transmit the trait to all their daughters but to none of their sons. Affected heterozygous women transmit the feature regardless of gender to half of their children. Affected homozygous women transmit the trait to all their children. Because women heterozygous or homozygous may be more women than men have the feature. The difference between the sexes is even greater when the disease is fatal in males. An X-linked dominant inheritance can be distinguished from an autosomal dominant inheritance is difficult if one considers only the inheritance pattern. There are large pedigrees required and because a transmission from man to man an X-linked inheritance excludes (men give only their Y chromosome to their sons on) is, pay particular attention to the children of affected men. X-linked recessive inheritance X-linked recessive inherited traits are transferred with the X-chromosome. Almost all affected people are male, because most women have a normal copy of the gene in question and are heterozygous with it. A typical family tree can be seen in X-linked recessive inheritance. X-linked recessive inheritance generally apply the following rules of inheritance: Affected are almost exclusively men. Heterozygous women are phenotypically normal as a rule, but as a feature-makers to transmit the abnormal gene to half of their children. Half of the sons of a feature wearer is affected, and half of daughters are characteristic wearers. An affected man never gives the feature to his sons on. All daughters of a man concerned feature wearers. Daughters of a wearer and a normal father are not affected, but half of them are winners. Although occasionally the disease is pronounced in heterozygous women with X-linked mutations, they are rarely as badly affected as men.