(a)[5]
Fill each gap with the most suitable word or letter. DNA contains the chemical elements carbon, hydrogen, oxygen, [BLANK] and [BLANK]. Two strands of DNA twist together to make a double [BLANK]. Each strand consists of a chain of [BLANK]. Bonds between paired bases keep the strands joined. These bases always pair in the same pattern: T with [BLANK] and [BLANK] with [BLANK].
(b)[5]
Explain how genetic modification may be used to alter the function of an enzyme so that it works on a different substrate.