Mendelian inheritance

A disease whose pattern of familial aggregation differs from that expected fi om the Mendelian inheritance of a single genetic defect. 

Mitochondria are unique organelles in that they contain their own DNA (mtDNA), which, in addition to ribosomal RN A (rRNA) and transfer RN A (tRNA)-coding sequences, also encodes 13 polypeptides which are components of complexes I, III, IV, and V (Anderson et al., 1981). This fact has important implications for both the genetics and the etiology of the respiratory chain disorders. Since mtDNA is maternally-inherited, a defect of a respiratory complex due to a mtDNA deletion would be expected to show a pattern of maternal transmission. However the situation is complicated by the fact that the majority of the polypeptide subunits of complexes I, III, IV, and V, and all subunits of complex II, are encoded by nuclear DNA. A defect in a nuclear-coded subunit of one of the respiratory complexes would be expected to show classic Mendelian inheritance. A further complication exists in that it is now established that some respiratory chain disorders result from defects of communication between nuclear and mitochondrial genomes (Zeviani et al., 1989). Since many mitochondrial proteins are synthesized in the cytosol and require a sophisticated system of posttranslational processing for transport and assembly, it is apparent that a diversity of genetic errors is to be expected. 

McKusick VA Mendelian Inheritance in Man. Catalog of Human Genes and Genetic Disorders, 12th ed. Johns Hopkins Univ Press, 1998. [Abbreviated MIM]... 

Online Mendelian Inheritance in Man (OMIM) Center for Medical Genetics, Johns Hopkins University and National Center for Biotechnology Information, National Library of Medicine, 1997. http //www.ncbi.nlm.nih.gov/omim/... 

This table indicates the chromosomal location of several genes and the diseases associated with deficient or abnormal production of the gene products. The chromosome involved is indicated by the first number or letter. The other numbers and letters refer to precise localizations, as defined in McKusick VA Mendelian Inheritance in Man, 6th ed. John Hopkins Univ Press, 1983. 

MIM = Mendelian Inheritance in Man. Each number specifies a reference in which information regarding each of the above conditions can be found. 

OMIM Home Page—Online Mendelian Inheritance in Man http //www.ncbi.nlm.nih.gov/omim/... 

Defects of nuclear DNA also cause mitochondrial diseases. As mentioned above, the vast majority of mitochondrial proteins are encoded by nDNA, synthesized in the cytoplasm and imported into the mitochondria through a complex series of steps. Diseases can be due to mutations in genes encoding respiratory chain subunits, ancillary proteins controlling the proper assembly of the respiratory chain complexes, proteins controlling the importation machinery, or proteins controlling the lipid composition of the inner membrane. All these disorders will be transmitted by mendelian inheritance. From a biochemical point of view, all areas of mitochondrial metabolism can be affected (see below). 

All disorders except those in group 5 are due to defects of nDNA and are transmitted by Mendelian inheritance. Disorders of the respiratory chain can be due to defects of nDNA or mtDNA. Usually, mutations of nDNA cause isolated, severe defects of individual respiratory complexes, whereas mutations in mtDNA or defects of intergenomic communication cause variably severe, multiple deficiencies of respiratory chain complexes. The description that follows is based on the biochemical classification. 

Mutations associated with inheritable diseases are numbered in MIM notation as described in McKusick, V. A. Mendelian Inheritance in Man. A Catalog of Human Genes and Genetic Disorders, 12th edn. Baltimore Johns Hopkins University Press, 1998. An updated Internet version is found at Online Mendelian Inheritance in Man, OMIM . McKusick-Nathans Institute for Genetic Medicine, Johns Hopkins University (Baltimore, MD) and National Center for Biotechnology Information, National Library of Medicine (Bethesda, MD), 2000, www.ncbi.nlm.nih.gov/ omim/. 

Search engine of the National Center for Biotechnology Information, including a few databases PubMed (MEDLINE biomedical literature), PubMed Central (free digital archive of life sciences journal literature), Books, OMIM (Online Mendelian Inheritance in Man, a catalog of genetically linked diseases),... 

OMIA (Online Mendelian Inheritance in Animals, a catalog of genetic diseases in animals), and others. 

It is clear from family studies that apo(a) gene polymorphism is a consequence of the autosomal codominant Mendelian inheritance of multiple alleles operating at a single chromosomal locus (G7, U4, U6). In families where this simple inheritance pattern was not followed, the existence of a null allele has been postulated (U4, U6). A null allele frequency of 6% was estimated for the subjects... 

McKusick, V. (1998) Mendelian inheritance in man catalogs of human genes and genetic disorders, 12th ed., Johns Hopkins University Press, Baltimore. 

Alzheimer s disease exists in two major forms, the so-called early and late onset types. The former follows typical Mendelian inheritance while the latter shows a more complex, non-Mendelian, pattern of inheritance. The early onset form of the disease has permitted the identification of several genes which are causally related to the condition. 

Three different rare genetic metabolic defects in sialic acid metabolism are known, as indicated in Fig. 4.3.2 [3, 21] (1) free sialic acid storage disease (SASD Online Mendelian Inheritance in Man, OMIM 604369, 269920), a lysosomal membrane transporter defect (2) sialuria (OMIM 269921), a feedback inhibition defect in sialic acid biosynthesis (3) sialidosis (OMIM 256550), a breakdown defect of sialyloli-gosaccharides caused by a defect of lysosomal sialidase. In all these genetic defects, an increased amount of sialic acid can be found in tissues and or body fluids, either bound to OGSs as in (3), or in its free state as in (1) and (2). 

NPC1 Niemann-Pick disease type Cl, NPC2 Niemann-Pick disease type C2, OMIM Online Mendelian Inheritance in Man, P plasma, U urine... 

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