What are Genetics Disorders ?
Genetics Disorders :
As hereditary diseases and characteristics are known, either by a gene ( monogenic ) or several atypical altered genes ( polygenic ) are triggered at certain morbidity and dispositions lead. In this context one also speaks of monogenic and polygenic disease . In a narrower sense to count only those features of the diseases and genetic diseases that are triggered by the start of atypical changes in genes and inheritance are transmitted from the ancestors to their descendants. Syndromes such as forms of trisomy , in which not the usual number of 46 chromosomes in the human genome is able, therefore, strictly speaking, are not counted as a genetic disease, because they usually occur spontaneously and are rarely inherited.
Various forms :
Hereditary diseases follow different inheritance patterns and are associated with different inheritance, repeat and disease probabilities. A distinction is autosomal recessive and autosomal dominant inheritance patterns of mitochondrial and gonosomal.
Autosomal recessive modes of inheritance :
The special feature will only become apparent when on each of two chromosomes (1 to 22, not the sex chromosomes X and Y) a change ( mutation ) in both copies of a particular gene is, that if the person in question in each case a change of its inherited biological father and biological mother of his. Parents must not be affected, the phenotype does not in any generation. The mutation need not be identical. If two distinct molecular genetic mutations to the same loss of function in a gene, it is called compound heterozygosity.
Causes of apparent discrepancies autosomal recessive inheritance:
- Nichteinrechnen heterozygotes with healthy children
- Pseudo-dominance
- Heterogeneity
- Isodisomy
Examples of autosomal recessive modes of inheritance:
- Phenylketonuria (PKU) (phenylalanine hydroxylase defect)
- Cystic fibrosis
- Albinism
- Complex heterozygosity
Autosomal dominant modes of inheritance :
This is already an altered allele (alleles are each respectively corresponding genes of a diploid chromosome set) to one of the two homologous chromosomes characteristic value. The genetic information is located on one of the 44 autosomes and is independent of prior sexual trait. Women and men are affected equally so. The phenotype appears in every generation. Examples include: Huntington's disease , retinoblastoma , polydactyly , and piebaldism .
gonosomal modes of inheritance :
Gonosomal hereditary diseases, ie those concerned, in which the change in the sex chromosomes X and Y are, in most cases on the X chromosome because the Y chromosome contains very few genes. The example of X-linked inheritance following features emerge:
X-linked dominant: boys / men are more affected because they have only one X chromosome (the mother). Girls / women are genotypic often affected, because the probability of obtaining an altered X-chromosome, with two X chromosomes (one from the father, one from the mother) is higher.
X-linked recessive: girls / women are affected only if both X chromosomes are damaged, otherwise they are only carriers ( female carriers ), ie they can change in X-chromosome pass on to their children, themselves form but in no corresponding phenotype . Girls / women can often compensate for the change to an X chromosome from their second X chromosome, if it is not changed. Boys / men are affected when they get a change in the X-chromosome of the phenotypically normal mother, or a modified two X chromosomes inherited from a phenotypically affected mother, as boys / men even of one X chromosome in each case the mother and have only got this one. Phenotypically boys / men are so often affected, as girls / women to compensate for the defect by the other X chromosome.
or mitochondrial patterns of inheritance Extrachromosomal
Approximately 0.1 percent of the DNA of a human cell are not in the nucleus, but in the mitochondria . Since oocytes in contrast to several hundred thousand sperm mitochondria possess mutations in the mitochondrial DNA is only inherited his mother. The same applies to the chloroplasts of photosynthetic organisms.
See also Extrachromosomal Inheritance
Diagnosis and Treatment :
On suspicion of a hereditary disease, a human genetic study of clarification. Here, the chromosomes to numerical and structural changes are reviewed. If there is suspicion for a specific genetic defect, a more extensive, elaborate study of individual Genkonstellationen is possible. The results can be useful for risk assessment with respect to an inheritance.
Therapy may present with a special feature of the genetic material, of course, had no influence on the causes, but only symptomatic measures are taken.
History :
In the first half of the 20th Century , the concept of genetic disease and is often used grossly inflated false, including for alleged "disease" as "criminal tendencies" or "antisocial behavior". This thinking influenced sterilization programs and euthanasia , thoughts, and found its extreme expression in the German National Socialism , but was at that time also in many other countries like the United States, England and France so far. Today, only such diseases are called genetic diseases that are most clearly delineated and go back with a very high probability of genetic defects.
