Why do red-haired people usually have so many freckles?

[eyedress]

Red hair and freckles are both influenced by the MC1R gene. MC1R codes for a protein that balances the two types of pigment present in hair and skin.

Remember that you get two copies of every gene from your parents — so you've got two copies of the MC1R gene. Whether both are funtional is a toss-up and varies from one person to the next.