Question: If someone with ginger hair and white skin reproduced with someone with black hair and black skin, what is the science behind the unlikelihood of giving birth to a black skinned ginger haired baby? Does this have any relation to the chromosomes? I'm curios to know as you can find any colour haired person with white skin but a limited colour of hair with a person with white skin, to me this does not make sense.

Helen Fletcher answered on 23 Jun 2011:

The genetics of hair colour is a complicated one! Hair colour is determined by the relative amounts you have of two pigments: eumelanin and pheomelanin. The more pheomelanin you have, the redder your hair. There’s a gene that converts pheomelanin into eumelanin, and to have red hair, you need a mutated version of this gene from both your mother and father; which means that red hair is pretty rare. If you inherit the mutated version from just one of your parents, the unmutated version from the other ‘covers up’ the effect, so the mutated version is there, but in secret. Someone with dark skin and dark hair is very unlikely to carry one of these ‘secret’ copies of the gene, meaning the child is very unlikely to inherit two such copies and have red hair.

Skin colour is bit simpler: people with very pale skin have two copies of a ‘light skin’ gene (one from each parent), and people with dark skin have two copies of a ‘dark skin’ gene. Inheriting one of each from each parent will give you a skin colour somewhere in the middle. But when someone with one of each of these genes has children, they can pass on either the light gene or the dark gene, so their baby could end up with darker or lighter skin than either of the parents. Well maybe that one wasn’t so simple after all…