Linkage analysis studies

Lastly, studies on the different polymorphic forms of the synapsins, that organize the mobilization of neurotransmitter vesicles thereby regulating neurotransmitter release, could account for some of the subtle changes in neurotransmission that occur in schizophrenia. However, to date linkage analysis studies have failed to reveal any positive associations between the various polymorphisms of the synapsin gene and schizophrenia. 

Linkage analysis by studying RFLP patterns in two or more generations of family members afflicted with a disease is useful for genetic counseling for the prediction of inherited disease, in spite of its limitations, such as the possibility of genetic recombination or the presence of more than one gene locus in different family members. 

Thus, the use of complementary approaches including heritability analysis, linkage analysis, expression studies, and association studies can be used to identify and characterize novel genes important in sensitivity and resistance to chemotherapy. Ultimately, one must consider validating the genes identified in an appropriate cell or tissue (Fig. 3). 

Another example is the study of microsatellites that are short DNA loci having simple sequence repeats that are widely distributed throughout the human genome. They are a valuable source for human genetic linkage analysis and molecular cancer research... 

For late onset diseases such as Alzheimer s disease, detection of genes is even more difficult, because parental information may be difficult or impossible to obtain. The use of siblings has the advantage of avoiding the difficulties of recruiting parents for the study of late-onset conditions. The utility of sib pairs for QTL linkage analysis is well established (17,18). If a marker locus is linked to a QTL the difference in the value of a trait between two sibs in... 

---