Going back to my high school days we were taught about dominant and recessive genes. We were taught how to calculate the geneotype and pheneotype of potential offspring using a small table (forgotten the actual table name). But it never occurred to me then what determines if a gene is dominant or recessive and how this is carried out biologically.
Take my example below, there is a 50% change that an offspring will carry both the tall (T) and short (t) genes. What determines that the tall gene T has a dominant effect over the short gene t.
Now, I know that there is going to be differences between the different genes (i.e. eye colour), but is there a general description any one and provide which states how a gene becomes dominant and how the dominant effect is carried out biologically.