Heritability broad

This value represents what is called the broad heritability. The model makes the usual assumptions no placement effects, no genotype x environment interaction and no genotype x environment correlations, adequate representation of genotypes and adequate representation of environments. The MZA correlation alone directly estimates the broad heritability. The correlation is not squared. 

Table 3. Median proportions of variance attributed to additive genetic, nonadditive genetic, shared environmental, and nonshared environmental effects plus error and broad heritability, derived from eight kinships, for seventeen brief strong vocational interest blank scales...

Trait MZA (59) DZA (47) MZT (522) DZT (408) Additive genetic Non-additive genetic Common environment Broad heritability... 

Table 10. Mean intraclass correlations and broad heritabilities of measures of psychopathology in two studies, one using twins reared together and the other using twins reared apart...

Until recently, only a few studies have utilized human lymphocytes or Epstein-Barr virus (EBV)-transformed lymphoblastoid cell lines (LCLs) derived from the CEPH to identify heritable traits related to drug sensitivity or other drug-induced pharmacodynamic parameters (3,4). However, these studies are providing evidence for the broad applicability of this approach to pharmacogenomic research. 

If the trait is caused partially by the environment, the mutation component is given by the broad-sense heritability of the trait. For a quantitative trait, the broad-sense heritability is the fraction of the variance of the trait that is genetically determined. For a rare qualitative trait, it is (to a satisfactory approximation) the fraction of the incidence that is genetically caused. Thus, when we do not know the exact genetic basis of a disease, we can estimate its mutation component by heritability measurement—by correlation and concordance between identical twins. For example, if the concordance of identical twins (preferably reared in different homes) is one-half for some rare trait, this is the estimate of the broad-sense heritability. There is always the problem that measures of heritability based on correlations between relatives are inflated by environmental correlations. In this report, however, we are concerned more with the societal consequences of underestimating the mutation component than of overestimating it, so environmental correlations are not as serious as in most genetic analyses. 

There is a problem with this analysis. As mentioned earlier, it is possible for a trait to be determined completely genetically—and hence to have a broad-sense heritability of 1—and still not depend on the mutation rate. We can get some further insights by using another kind of heritability, narrow-sense heritability. Roughly, this is the proportion of the phenotypic variance that is genetically transmitted from parents to children. 

Broad-sense Heritability Narrow-sense Heritability Nutation Component Paradigm Example... 

We can summarize these conclusions as follows If narrow-sense heritability is high (and broad-sense heritability is high a fortiori), the trait has an equally high mutation component. An increase in mutation rate will eventually lead to a proportional increase in impact. 

If broad-sense heritability is high, but narrow-sense heritability is low, the mutation component is indeterminate. However, an increase in mutation rate will not have an appreciable effect for a very long time, if ever. 

If broad-sense heritability is low (and narrow-sense heritability necessarily is low), the trait is at most very slightly responsive to a change in mutation rate. If there is a change in impact, it will be spread over a very long time. 

HERITABILITY A concept that quantifies the proportional contributions of genotype and environment to some trait broadly, the proportion of the phenotypic variance in a population that is attributable to genetic differences among individuals in the population narrowly, the proportion of the phenotypic variance that is attributable to additive genetic variability (i.e., the proportion of phenotypic deviation from the population mean that is transmitted to the next generation). 

What, then, of the claim that individual differences in intelligence are subject to strong genetic influence We will hear summaries of findings from twin and adoptee studies indicating a substantial broad heritability. Most reviewers have put the figure somewhere in the 40—80% range (Hunt 1997, Waldman 1997) but, from both theoretical and practical perspectives, it matters little just where in that... 

If there are also non-additive effects, h2 = Vg/Vp defines broad heritability or degree of genetic determination. 

Autism and the related disorders Pervasive Developmental Disorder Not Otherwise Specified (PDD NOS) and Asperger syndrome (AS) are neurodevelopmental conditions with strong heritability (Muhle et ah, 2004) characterized by impairment in social-communicative skills and a restricted and repetitive pattern of interests and behaviours. Together they are broadly referred to as autism spectrum disorders (ASD) (APA, 2000). 

A multinational study conducted with more than 100 rice cultivars showed that the allelo-pathic rice cultivars behaved similarly in different geographical locations, indicating that the traits were more influenced by genetics than environmental conditions. This allelopathic trait appe ars to be inherited [ 111 ]. A study on broad-sense heritability of the ability of rice to reduce the root growth of bamyardgrass produced a value of 0.85, which is above the threshold required by breeders to screen for a trait. Quantitative Trait Loci (QTL) analysis of allelopathic cultivars indicates that a third of the total variation for the allelopathic phenotype in a large population of inbred rice lines was accounted for by four QTLs located on three separate chromosomes [108]. 

Estimation of genotypic variance ccmponent and broad-sense heritability EBLUPs cfgenctypic effects and predicticn of the genetic gain. 

Estimates for the coefficient of genotypic variation and broad-sense heritability are then obtained. All analyses are guided by the objectives described in the following subsections. 

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