. it's in every cell in the body along molecule that looks like a twisted rope ladder and it contains all the instructions for making a human being. its rungs are made up of four different building blocks you can think of them as letters that can be used to create an infinite number of words what we call genes that endless variety and the d.n.a. is what makes each and every one of us unique. some sections of d.n.a. are like the different departments in a company that keep business ticking over listen for instance borders to the cells manufacturing facilities to make and deliver more of this or that product. the instructions in coded in d.n.a. are used to make a vast array of proteins and they control every aspect of metabolism and the body.