The Complexity of Hereditarbility Scores Explained  -

          Hereditability relates to a correlation, which measures the differences between two sets of statistics, measures. It could be measuring the differences between two days of temperature every hour. If the temperatures are identical on the two days, if the gap between the two temperature are the same every hour,  then two lines will remain identical on a graph. They would resemble the gap between two railway lines. A perfect correlation will be 1, 100%.

      In hereditability, what is measured is the variance the difference between the subjects, the traits. The hereditability of identical twins who share the same genes, they are clones, will be 0 , 0%. 

      There will be no significant genetic difference between the twins. All the differences will be environmental, not genetic.

      If a diverse genetic range of grass seed was placed in a tray and grown in identical environmental growing conditions, then the differences in the height of grass would be attributed to genetics. The score would be 1, a 100%.

    If an genetic identical sets of seeds was placed in a tray, then any differences in height would be due to the environment. The score would be 0, 0%.    

      The fact that height say has a hereditary score of 70% does not mean that 70% of persons height is attributable to genes and 30% environment. Hereditaribily refers to the difference in height.

       If the diverse grass seed grows to 10 cms and the heritability is say 50%,  and the spread of height is 6 to 10 cms, then the difference would be 4 cms. 2 cms of the difference would apply to genes and the environment respectively.

      if  the  heritability score is 75% the be 3 cms and 1 cms respectively.

        Plomin geneticist states in the T.E.S that:-

       "A useful example from Blueprint is that heriditability for weight is 70%. But that does not mean that your weight is 70 % cent down to your DNA. Instead, it means that 70 per cent of the differences between the weight of individuals across a population – the variability – is down to differences in DNA."

     Hereditability scores are not constant. Genes cannot exist without an environment. The more children are given equitable learning environments in school the more the heriditability, genes will account for the differences.

      Identical twins share the same genes. It possible through making comparisons is between them to work out the correlations between them. Their I.Q. and personality highly correlate strongly according to Plomin.

  Hereditrability score about populations, not individuals. They are averages. They are probabilities.

       The probabilities relate to averages. The conform to the standards distribution curve. RR.

        The hereditability of breast cancer in women is xx. Even if two identical twins have the genes that increase the risk of their having cancer, it does not necessarily mean that one or either will have the illness.

      The polygenic score is the risk that can be established through D.N.A.  It is not a precise measure. It does explain what behaviours and characteristicts exist amongst populations

          Genetics is not deterministic, but it does set the parameters of behaviours and capabilities.

   B. Child genisus have acceptional talent. it cannot be achieved simply through hard work.