Guanine is always base pair with____

Answer

**Step-by-Step Solution:**

1. **Identify the Nitrogen Bases**: In DNA, there are four main nitrogen bases: adenine (A), thymine (T), cytosine (C), and guanine (G). In RNA, uracil (U) replaces thymine.

2. **Understand Base Pairing**: The nitrogen bases pair in a specific manner. Adenine pairs with thymine (or uracil in RNA) and guanine pairs with cytosine.

3. **Determine Guanine's Pair**: According to the base pairing rules, guanine (G) always pairs with cytosine (C). This pairing is due to the formation of hydrogen bonds between them.

4. **Count the Hydrogen Bonds**: Guanine and cytosine form three hydrogen bonds, which makes their pairing more stable compared to adenine and thymine, which form two hydrogen bonds.

5. **Conclusion**: Therefore, guanine is always base paired with cytosine.

**Final Answer**: Guanine is always base paired with cytosine.

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