Recent stories in the news about blond children being found in dark-haired and dusky-skinned Romany families -- children that weren't biological offspring -- prompted us to ask: Is it possible for two children from the same family to look completely different? It turns out the answer is, yes, it is possible. Here's how.
Nature is absolutely amazing when it comes to reproduction. There is a system specifically designed to make children different.
A person has a set of chromosomes. Each chromosome contains two halves that join in the middle so they look like an "X." All that a chromosome is, by the way, is two very tightly coiled strands of DNA (deoxyribonucleic acid).
The two halves of each chromosome come from the two parents. One half of the "X" in each chromosome comes from the mother, and the other half comes from the father. The two halves are bonded together at the middle of the "X." Each half of the "X" contains a complete set of genes, so each chromosome has two copies of every gene -- the "dominant" gene of the two is the one that is expressed.