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chazwomaq t1_jb09sjt wrote

>The way I read that 100% heritable corresponds phenotype dependent 100% on genes

This is not correct. It means 100% of the phenotypic variation depends on genes, which is quite different. As a classic example, the heritability of "leggedness" in humans is very low, close to 0. This is because when people don't have two legs, it is usually for environmental reasons (accidents, amputation etc.). However, I'm sure you would agree that having two legs is specified in the human genome.

Heritability is not a conditional probability as you describe it (I know of no such statistic, although I suppose you could empirically calculate one). It is more like a r^2 value in statistics if you are familiar with that.

Another note - h^2 is not necessarily fixed, and only applies in a particular environmental context. Change the environment, and you could in theory change h^2.

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SerialStateLineXer t1_jb0vxw2 wrote

>It means 100% of the phenotypic variation depends on genes, which is quite different.

More precisely, it usually refers to share of the variation within the specific population being studied. For example, when measuring the heritability of height in a wealthy country, you will get a very high heritability estimate, perhaps 0.8-0.9. When measuring the heritability of height in a global population, you'll get a lower heritability estimate, because a significant fraction of your sample will have had their growth somewhat limited by environmental factors like undernutrition or disease. Conversely, if you're studying a population of clones, the heritability will be zero, because there's no genetic variation and all variation must be due to environment.

None of these estimates is more correct than the other, because heritability can only be defined for specific populations with specific distributions of genetic and environmental factors. There is no "ideal heritability."

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Chance_Literature193 OP t1_jb1vlb5 wrote

>It means 100% of the phenotypic variation depends on genes, which is quite different.

I think this is what I was trying to say, but let me restate it to make sure I am on the right track. 100 heritability implies variation in trait amongst a population is wholly accounted for by variation in genetics of population and there is no correlation between variation in environment causing additional variation in traits.

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chazwomaq t1_jb23r2v wrote

>100 heritability implies variation in trait amongst a population is wholly accounted for by variation in genetics of population

Correct.

>and there is no correlation between variation in environment causing additional variation in traits.

I would phrase it as "environmental variation does not cause additional variation in the trait".

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