458 CHAPTER 17 however, Limitations of heritability of individ As stated regions

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458 CHAPTER 17 however, Limitations of heritability of individ As stated regionsw are referre quantitati basic biol ity to ider severelv li ods until TABLE 17.2 1. Heritability does not indicate the degree to which a characteristic is genetically determined 2. An individual does not have heritability. There is no universal heritability for a characteristio. 3. 4. Even when heritability is high, environmental factors can influence a characteristic. 5. Heritabilities indicate nothing about the nature of population differences in a characteristic MAPPI ers have lar techni Another argument based on a misconception about heri- tability is that ethnic differences in measures of intelligence analysis. are genetically based. Because the results of some genetic genetic m studies show that IQ has moderately high heritability, and because other studies find differences in average IQ among ethni f a arti the inher phenotyp cally link a QTL c groups, some people have suggested that ethnic dif- terences in IQ are genetically based. As in the example of the effects of diet on human height, heritability provides no information about causes of differences among groups; it in only the degree to which phenotypic variance with na single group is genetically based. High heritability for detection dicates It is i rather, a g ethnicthat phenotypic differences groups are genetic. We should also remember a identifie n genetic and environmental effects in humans specific g specihc c does not mean that phenotypic differences is associs that separating is very difficult, so heritability estimates themismmarized was us unreliable. These limitations of heritability are su in Table 17.2. mmarized was use of corn. ing a va (Figure TRY PROBLEM 20 CONCEPTS

Explanation / Answer

1. Heritability does not indicate the degree to which a characteristic is genetically determined.

This means that one cannot exactly tell the number of genes or the type of genes that are involved in causing a trait. It can not identify if there are any missing factors or missense mutations that are involved in causing the trait. Rather, it can only determine if genetic factors are involved in causing a trait.

2. An individual does not have heritability

Individuals do not have heritability, but traits have heritability m which determine if genetic factors are involved in causing that particular trait.

3. There is no universal heritability for a characteristic

There is no universal heritability for a characteristic since expression of a particular trait or gene depends upon the environmental factors. Since, we cannot estimate with trait would be inherited and what factors from the environment would influence it, hence no universal standards could be added to the same.

4. Even when heritability is high, environmental factors can influence a characteristic

When heritability is high, it often means that one particular trait has been affected by genetic factors, heritability is affected by variance. This has been shown by the gene environment studies, especially twin studies, where, even after identical twin being used, difference in the environment would cause difference in the traits of the individuals. Example: height of humans.

5. Heritabilities indicate nothing about the nature of population differences in a characteristic.

Heritability will only give the degree to which a phenotype of an INDIVIDUAL is affected by the genes rather than the environmental factors.

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