Is it possible for an interracial couple (White, Black) to produce a child that has the same skin colour as the parents (white or black), or will the child always be a colour that is the “sum” of both parents (Brown)?
Answer David, Typically, the child is a “blend” of genes that can be either dark or light because skin color is determined by multiples of the same gene (we aren’t sure how many, but the latest estimate is about six). Skin color is an example of an additive trait, in which multiple genes add up to a certain dosage, so the sum effect depends on the number of genes that express the trait. For example, if skin color is determined by six identical genes, and we have two copies of each gene, then there are twelve possible contributions to the skin color trait. So, any one person can have from zero to twelve “dark” genes that give varying dosages of color. (Light skin is the mutant form of skin color, so most people have at least one or two dark genes.) When two people have a child together, the child receives half (or 6 of 12) of each parent’s skin color genes randomly. So, if the child randomly receives all dark genes from a parent that has 6 of 12 genes that are dark and all light genes f
