If on one helix of DNA the base is cytosine the other helix could have

Options

A. adenine
B. guanine
C. thymine
D. uracil

Answer

To solve the question, "If on one helix of DNA the base is cytosine, the other helix could have?" we can follow these steps:

### Step-by-Step Solution:

1. **Understand DNA Structure**: DNA is composed of two strands that form a double helix. Each strand consists of nucleotides, which include a sugar, a phosphate group, and a nitrogenous base.

2. **Identify the Base Pairing Rules**: In DNA, specific nitrogenous bases pair with each other according to base pairing rules:
- Adenine (A) pairs with Thymine (T) through two hydrogen bonds.
- Guanine (G) pairs with Cytosine (C) through three hydrogen bonds.

3. **Determine the Complementary Base**: Given that one helix has the base Cytosine (C), we need to find its complementary base on the other helix. According to the base pairing rules, Cytosine pairs with Guanine (G).

4. **Conclude the Answer**: Therefore, if one strand of DNA has Cytosine, the complementary base on the other strand must be Guanine.

### Final Answer:
The other helix could have Guanine.

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