Final answer:
The complementarity rule used in transcription is similar to the base complementary rule, except that uracil substitutes for thymine in RNA.
Step-by-step explanation:
The complementarity rule used in transcription is similar to the base complementary rule, except that uracil substitutes for thymine in the RNA. The complementarity rule states that only certain types of base pairing are allowed, where a certain purine can only pair with a certain pyrimidine. In DNA, adenine (A) pairs with thymine (T), and cytosine (C) pairs with guanine (G). However, in RNA, uracil pairs with adenine instead of thymine.