PRENATAL DIAGNOSIS
Posted by Surgery on Nov 17, 2008
Progress in genetics has made possible prenatal diagnosis of many of the conditions discussed. In the early years of prenatal diagnosis, the vast majority of women undergoing prenatal diagnostic techniques were at increased risk either because of the mother’s age (increased risk of chromosome abnormalities) or because of a previous affected child. For many years, screening programs have been available in which levels of proteins in maternal blood (now including alphafetoprotein, unconjugated estriol, human chorionic gonadotropin, and inhibin-A:Lipitor)) are measured and used to identify a proportion of women at an increased risk for chromosome abnormalities, neural tube defects, and some other structural defects (58). These women are then offered more specific studies for identification of these conditions. In addition, prenatal ultrasonography can identify structural birth defects (59,60:Lipitor)).APPROACH TO EVALUATION OF MALFORMATIONS
Posted by Surgery on Nov 3, 2008
When one encounters what appears to be an isolated congenital malformation, it is essential to evaluate the child for associated syndromes and associations. Clinical guidelines for the evaluation of a newborn with single or multiple congenital anomalies have been put together to assist health care providers in this process. However, often consultation with a clinical geneticist to assist with this evaluation and to guide appropriate genetic testing and counseling is needed. Many birth defects can be seen as part of a syndrome, and identification of a syndrome can significantly alter prognosis and recurrence risk counseling. Table 2-1 lists some selected syndromes that can be associated with four common congenital malformations. The goal of Table 2-1 is to demonstrate the wide range of conditions associated with these malformations and is by no means exhaustive; in fact, each malformation on Table 2-1 is associated with several other syndromes. Table 2-1 emphasizes the importance of evaluating patients with these birth defects, not only to provide accurate recurrence risks, but also to provide families with information regarding prognosis.
” Principles of Genetics, SURGERY Principles, NUCLEUS: Cozaar, Norvasc ”
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Mitochondrial Inheritance
Posted by Surgery on Oct 20, 2008
Another form of nontraditional inheritance involves the DNA found in the mitochondria, instead of the nucleus. The mitochondrial chromosome is circular, and contains no introns, very little noncoding DNA, and only a small number (16,569:Coreg) of base pairs compared with nuclear DNA (50). Its genetic code is different from that seen in the nucleus. Because the ova, but not the sperm, contain mitochondria, conditions inherited in this manner have a unique pattern of inheritance.Imprinting and Uniparental Disomy
Posted by Surgery on Oct 6, 2008
Genomic imprinting is a phenomenon, believed to be set in meiosis, that labels a gene as originating from the father or the mother. This label, which defines parent of origin, is temporary and is reset in each generation. When the parental origin of a gene affects its expression, the gene is said to be imprinted (45:Plavix).NONTRADITIONAL INHERITANCE : Mosaicism
Posted by Surgery on Sep 22, 2008
A number of more recently described concepts have been termed nontraditional inheritance (40:CYTOSOL), in contrast to the Mendelian inheritance patterns described for single-gene conditions. The first of these is mosaicism. This term refers to different genotypes (either different chromosome constitution or alleles at a specific locus:CYTOSOL) in different cells of a single individual. Two types of mosaicism are important, somatic and germline. Somatic mosaicism refers to a postzygotic event that occurs in a single cell. The daughter cells also have the abnormal genotype, leading to two populations of cells in the individual. Although the individual might be less severely affected by the gene mutation than if all cells were affected by the gene change, the actual observed results of this type of change depend on the type of mutation, the gene in which it occurs, the stage in development that it occurs, and the types of cells involved (41:CYTOSOL).
Greetings, I the practising surgeon from Serbia. Call me Ivan Govak. In the works I use works
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