Out of A-T,G-C pairing bases of DNA may exist in alternate valency state owing to arrangement called

Options

A. analogue substitution
B. tautomerisational mutation
C. frameshift mutation
D. point mutation

Explanation

**Step-by-Step Solution:**

1. **Understanding Base Pairing in DNA**: DNA consists of four nitrogenous bases: Adenine (A), Thymine (T), Guanine (G), and Cytosine (C). The base pairing rules state that A pairs with T and G pairs with C.

2. **Exploring Alternate Valency States**: The question refers to the ability of these bases to exist in alternate valency states. This means that the bases can adopt different structural forms under certain conditions, which can affect their pairing.

3. **Introducing Tautomerization**: The phenomenon that allows bases to exist in alternate valency states is known as tautomerization. Tautomerization is a process where a compound can exist in two or more structural forms (tautomers) that readily interconvert.

4. **Keto-Enol Tautomerism**: In the context of DNA bases, tautomerization often involves keto-enol isomerism. For example, the keto form of thymine can convert to its enol form, which can lead to mispairing during DNA replication.

5. **Impact on DNA Structure**: When tautomerization occurs, it can result in the incorrect pairing of bases (e.g., G pairing with T instead of C), which may lead to mutations. This is significant in the context of genetic variation and inheritance.

6. **Conclusion**: Therefore, the arrangement that allows A-T and G-C pairing bases of DNA to exist in alternate valency states is called tautomerization.

**Final Answer**: Tautomerization.

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