Answer the following question given this paragraph: 

The inheritance of traits is not always as simple as Mendel's rules. Each characteristic Mendel investigated was controlled by one gene that had only two possible alleles, one of which was completely dominant over the other. We now know that inheritance is often more complicated than this. In blood types, for example, there are actually three alleles instead of two. And some traits even have more than three alleles.


Q: What measures the amount of matter in an object?


A:
mass