Dizygotic

The concordance rate of mood disorders is 60-80% for monozygotic twins and 14-20% for dizygotic twins. Linkage studies suggest that certain loci on genes and the X chromosome may contribute to genetic susceptibility of bipolar disorder,... 

The difference between the MZA correlation and the MZT correlation estimates the magnitude of common or shared environmental influence. Models for dizygotic twins reared apart (DZAs) and dizygotic twins reared together (DZTs) would make use of a correlation of. 5 between the additive genetic components because such twins share half their segregating genes in common by descent. 

Moloney, D. P., Bouchard, T. J., Jr., Segal, N. L. (1991). A genetic and environmental analysis of the vocational interests of monozygotic and dizygotic twins reared apart. Journal of Vocational Behavior, 39, 76-109. 

Carrier of an autosomal recessive (Optional) Dizygotic twins... 

Concordance rates are compared in monozygotic (identical) and dizygotic (fraternal) twins to assess the contribution of genes to a trait These rates can be used to estimate heritability, the proportion of variation in a trait caused by genes. 

Twin studies comparing mono- and dizygotic twins have shown concordance rates of between 25 and 87%, depending on the study. Since none of the studies show a concordance rate of 100%, it is clear that non-genetic factors must influence the expression of OCD. 

DA, dopamine DD, depressive disorders (major depression and/or dysthymia) DZ, dizygotic twins 5-HT, serotonin p-CIT, iodine-123-labeled 2p-carbomethoxy-3p(iodophenyl) tropane MDD,major depressive disorder MRI, magnetic resonance imaging MZ, monozygotic twins NC, normal controls PC, psychiatric controls PTSD post-traumatic stress disorder rCBF, regional cerebral blood flow SPECT, single photon emission computerized tomography Tc HMPAO, technetium-99m hexamethylpropylene amine oxime. 

Tourette s Syndrome is a familial disorder (Pauls et ah, 1991 Walkup et ah, 1996). Twin and family studies provide evidence that genetic factors are involved in the vertical transmission within families of a vulnerability to TS and related disorders. The concordance rate for TS among monozygotic twin pairs is 50% while the concordance of dizygotic twin pairs is about 10% (Price et ah, 1985). If co-twins with chronic motor tic... 

There is an extensive literature showing that this disorder has a familial and hereditary pattern (42, 43, 44 and 45). Therefore, the genetic relatives of schizophrenic patients have an increased risk of developing this disorder. Several reviews of twin studies find that 30% to 65% of monozygotic twins are concordant for schizophrenia, in contrast to 0% to 28% of dizygotic twins (46, 47, 48, 49, 50, 51 and 52). 

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