How can a mutation occuring in a human be passed from parent to offspring? Where does it occur?

By defects on the single germ lines in the reproductive cells.

Mutations can be caused by ultraviolet radiations from the sun or is the DNA copies itself during cell division. However, acquired mutations in somatic cells (cells other than sperm and eggs) cannot be passed to the offspring. When mutations occur in reproductive cells and are called germ line mutations. A single germ line can have a range of defects.