Genes are tiny structures inside cells that control the growth and change of cells  They are like a series of instructions that build an organism and enable it to function properly  From tigers to toadstools (a poisonous mushroom) to humans, every organism contains genes in its cells  Your genes determine how you look, from the color of your hair to the lack of a tail, everything is genetically determined
Obviously, your environment can also affect how you look, but genes are decisive
Genes determine the appearance of an organism