These events take place during transcription. 1. Bonds are broken between complementary bases. 2. Bonds are formed between complementary bases. 3. Sugar-phosphate bonds are formed. 4. Free nucleotides pair with their complementary nucleotides. Before the mRNA molecule leaves the nucleus, which of these events will have happened twice?
- A1, 2, 3 and 4
- B1, 3 and 4 only
- C2, 3 and 4 only
- D1 and 2 only