During the process of transcription, a portion of a DNA molecule is used to create a mRNA Molecule. DNA stores genetic information in the nucleus of your cells. When RNA molecules are produced it happens inside the nucleus. The RNA molecule can then leave the nucleus and travel to ribosomes which are located in the cytoplasm and attached to endoplasmic reticulum. The RNA will be used to create proteins molecules.
This can happen because you have recessive and dominant characteristics passed down. So you can get a totally different chromosome that doesn't come from your parents because your grandparents may have had it or great grand parents, the line keeps going .