Amutation changes the dna sequence aagcctggcaat to the new sequence aagcctgcgcaat. what kind of mutation has occurred?
a. deletion
b. insertion
c. duplication
d. substitution

The excess of DNA is due to b. insertion

For example of an insertion mutation:

The Klinefelter syndrome is caused by an insertion mutation. It occurs when there is an existence of an excess or extra X chromosome in each cell that may cause an abnormality in the development of males. It usually affects the physical and cognitive development of male with symptoms varying from one person to another.  Kids with these type of disorder may experience  learning disabilities and even speech and language  problems.  These kids tend to be quiet and very sensitive. They can also be very passive.