DNA stores information in a sequence of adenine, cytosine, guanine and thymine on a backbone of two deoxyribose molecules, which intertwine in a double helix. In nature, this information is read by RNA molecules and turned into proteins.
Answer:
Having a repetitive enzyme system would allow more than one enzyme to catalyze a particular reaction. If one of the types of enzyme is not able to perform its function due to temperature or any other factor, then another kind of enzyme would be able to catalyze the reaction. Hence, having repetitive enzyme systems is very effective in carrying out the metabolic functions of the body even when conditions are not favourable.
Because Thymine is "replaced" with Uracil, the corresponding RNA Code for AAT would be UUA.