Certain situations represent different patterns of inheritance, often because the genes or chromosomes are changed. However, some of these changes, such are. As the mosaic relatively common. Others, such as polymorphisms, are so common that they can be regarded as normal variants mutations and polymorphisms: variations in DNA can occur spontaneously or in response to cellular damage (. Eg radiation, mutagenic drugs, viruses). Some of which are repaired by the DNA error-correcting mechanisms of the cell. Other variants are not fixed and can then be passed on to replicated cells; In such cases, the variation is called a mutation. However, the offspring can only inherit the mutation if the bacterial cells are affected. Defined mutations can occur only once in a person or a family. Most mutations are rare. Polymorphisms begin as mutations. They are variations in DNA that are common in a population (with a prevalence of ? 1%) by sufficient transfer or other mechanisms. Most polymorphisms are stable and do not change significantly the phenotype. A common example, the blood types (A, B, AB and O). Mutations (including polymorphisms) are random changes in the DNA. Many mutations have little impact on cell function. Some mutations alter cell function, often in a harmful way, and some are lethal to the cell. Examples of adverse changes in cell function mutations that cause cancer by producing oncogenes or activate or tumor suppressor genes change (Cellular and molecular mechanisms of malignant tumors: molecular changes). Rarely a change means a survival advantage in cell function. These mutations are passed on to offspring. The mutation that causes sickle cell anemia, gives both resistance to malaria. This resistance was a clear survival benefit in areas where malaria was endemic and often deadly. But the fact that symptoms and complications of sickle cell anemia show the mutation also has an adverse effect if it occurs homozygous. When and to what type of cell mutations occur, certain anomalies can explain the inheritance patterns. Typically, one would expect that an autosomal dominant disorder is present in one or both parents of an affected person. However, some diseases in the autosomal dominant inheritance seemingly new (de novo) may occur (in people whose parents have a normal phenotype). About 80% of patients with achondroplastischem dwarfism have never been available before dwarfism in the family, so it is a new mutation Many of these people is the cause of a spontaneous mutation, which occurs at a very early stage of embryonic. In this case, other descendants have no increased risk for this disease. However, for some of them the interference with their parents (z. B. an autosomal dominant gene in one parent with normal phenotype) developed by a germ cell mutation. If this is the case, other offspring to inherit the mutation is an increased risk. Mosaic A mosaic occurs when a person develops from a single fertilized egg ? 2 cell lines with different genotypes. A mosaic is the normal consequence of a X-inactivation in females (factors influencing gene expression: chromosome inactivation). For most women, some cells an inactive maternal X, and other cells have an inactive paternal X. mosaics can also result from mutations. Mutations can occur in any large multicellular organism during cell division. Every time a cell divides, find expected to take 4 or 5 changes in the DNA. Since these changes are passed on to subsequent cells produced, have large multicellular subclones of cells that have slightly different genotypes. A mosaic can be the cause of diseases in which patchy changes occur. When McCune-Albright syndrome can suffer. B. to patchy dysplastic bone changes, abnormalities of endocrine glands, pigmentation, and occasionally heart or liver abnormalities. A McCune-Albright mutation in all cells would result in early death, but it is because the diseased supported by normal tissue, people can survive with genetic mosaic. Occasionally, the light form a Einzelgenstörung seems to be with one parent, while in reality it is a mosaic. If children have received a nucleus with the mutant allele, so that the abnormality is present in all cells, they are more affected. Chromosomal abnormalities are usually fatal to the fetus. However, a chromosomal mosaic in some embryos occurs, which leads to some chromosomally normal cells, making it possible that the offspring are born alive. Chromosomal mosaics can be identified based on prenatal genetic testing, in particular by chorionic villus sampling. Extra or missing chromosomes Abnormal numbers of autosomes usually result in serious abnormalities. For example, additional autosomes cause abnormalities such as Down’s syndrome and other severe syndromes or lead to fetal death. The lack of an autosome is usually fatal to the fetus. Chromosomal abnormalities (chromosomal and gene abnormalities) are usually diagnosed before birth. Due to the X-chromosome inactivation an abnormal number of X chromosomes is usually much less severe than an unusual number of autosomes. For example, the anomalies which result from the absence of an X chromosome, usually relatively small (eg. B. Turner syndrome, Turner syndrome). Women with three X chromosomes (trisomy X aberrations of sex chromosomes) are often physically and mentally normal; only one X chromosome of the genetic material is fully active, even if a woman has> two X chromosomes (the extra X chromosomes are partially inactivated). A uniparental disomy uniparental disomy occurs when a chromosome pair is inherited only from one parent. It is very rare and is considered a rescue attempt of trisomy: a zygote originally lost trisomy (3 instead of 2 of a specific chromosome), and one of the three comes. This is a process that leads to uniparenteraler disomy when the two remaining chromosomes come from the same parent (this occurs in one third of cases). Uniparental disomy can cause abnormal phenotypes and inheritance pattern. In addition, z can. As well as duplicates of the same chromosome (isodisomy) be present, and should carry an allele for an autosomal recessive disease that affected have under certain circumstances, an autosomal recessive disease, although only one parent is a carrier. Uniparental disomy can lead to a disturbance formative when the disomic chromosome loss of appropriate expressions of a critical embossed area leads (z. B., the Prader-Willi syndrome from maternal isodisomy of chromosome 15 occur). Chromosomal translocation chromosomal translocation is the exchange of chromosome parts between unpaired (non-homologous) chromosomes. If chromosomes exchange parts of the same genetic material, the translocation as balancing will be described. Unbalanced translocations result in the loss of chromosomal material, mostly the short arms of two connected chromosomes, so that only 45 chromosomes remain. Most people with translocations are phenotypically normal. However, translocations can cause leukemia or cause (acute myelogenous leukemia [AML], but also chronic myeloid leukemia [CML]) or Down’s syndrome. Translocations increase the risk of chromosomal abnormalities in children, especially in non-balanced translocations. Because chromosomal abnormalities are often fatal for an embryo or a fetus, a parental translocation can lead to unexplained recurrent miscarriages or infertility. Trinucleotide repeat disease, the trinucleotide repeat disease arises when a triplet of nucleotides in an abnormal number within a gene is repeated (sometimes up to several hundred times). The number of trinucleotides can increase if the gene is transferred from one generation to the next, or when cells divide in the body. If the number of trinucleotides increased enough, Gene cease to function normally. Trinucleotide repeat diseases are not common, but occur in neurological diseases (eg. As in myotonic dystrophy or Fragile X syndrome) and especially those with CNS involvement at (z. B. Huntington’s disease). Trinucleotides can be detected by techniques such as DNA analysis. An anticipation anticipation is when a disease begins in each successive generation in even earlier age and increasingly makes its appearance. It could be for. Example, be an anticipation, if one parent has a chromosomal mosaic and have all of the child cells, the full mutation. Anticipation may also be that at a trinucleotide repeat disease the number of repeats increases and therefore the expression of the phenotype from generation to generation is stronger. Key points A seemingly autosomal dominant mutation can arise spontaneously and can not show an increased risk in siblings. Slight changes in disturbances may reflect mosaicism. Chromosomal translocations may have no phenotypic effects, but lead to leukemia, Down syndrome, miscarriage or chromosomal abnormalities in the offspring. Hereditary diseases can be severe and earlier break in life, with successive generations, sometimes due to triplet-repeat diseases.

Health Life Media Team

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