bobrilla

okay, thank you for your answers! what confused me at first was how this subject is taught at school and in books. Talking about THE DNA of someone is pretty confusing. Why not saying it is a group of molecules for example?

how can it be same molecule in each chromosome if it has different size and different number of genes ?

I am trying to understand if a chromosome is made of one DNA molecule or just a part of a DNA molecule. Maybe i am confused with the DNA molecule itself. The way it is taught seems to indicate that each human beings has DNA molecules that are all the same. Then how can the same molecule make different chromosome with different size?