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 .
Lungs, lung cells, lung tissues
Gregor Mendel found out that treats depends on inherited factors. Also, he study science and math. He then study inheritance of treats and beginning to experiment. So, then he discover that traits depend on inherited factors while he experiment with peas. He had a garden to test with pea plants.