The structure of DNA with labeled parts: sugar, phosphate group, and nitrogenous bases (adenine, thymine, cytosine, guanine).

It looks like you've uploaded an image of a DNA structure diagram that is partially labeled, and it appears to be a worksheet or educational activity. The goal seems to be to label the components of the DNA double helix, particularly identifying the nitrogenous bases and their complementary pairs.

Let’s go through the structure of DNA and solve this step by step.

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🔬 Structure of DNA: Key Components

DNA (Deoxyribonucleic Acid) is a double helix made up of two strands that run in opposite directions (antiparallel). Each strand consists of repeating units called nucleotides, each containing:

1. Sugar – Deoxyribose
2. Phosphate group
3. Nitrogenous base

The two strands are held together by hydrogen bonds between complementary nitrogenous bases:

- Adenine (A) pairs with Thymine (T) (2 hydrogen bonds)
- Guanine (G) pairs with Cytosine (C) (3 hydrogen bonds)

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🧩 Analyzing the Diagram

Looking at your image:

- On the left side, there's a backbone made of alternating sugar and phosphate groups.
- On the right side, there are labels:
- SUGAR
- PHOSPHATE GROUP
- ADENINE
- THYMINE
- CYTOSINE
- GUANINE

But the bases on the ladder rungs (the horizontal lines connecting the two strands) are not yet labeled.

Each "rung" represents a base pair. The task likely involves matching the correct base pairs.

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✔ Step-by-Step Solution

We need to fill in the missing nitrogenous bases so that they follow the base pairing rules:

- A ↔ T
- G ↔ C

Now let’s assume the vertical columns represent the two strands of DNA. The horizontal bars (rungs) connect the bases.

Let’s suppose the top strand has bases (from top to bottom):

1. Adenine (A) → must pair with Thymine (T)
2. Guanine (G) → must pair with Cytosine (C)
3. Thymine (T) → must pair with Adenine (A)
4. Cytosine (C) → must pair with Guanine (G)
5. Adenine (A) → must pair with Thymine (T)
6. Cytosine (C) → must pair with Guanine (G)

So, the bottom strand (opposite) should have:

1. T
2. C
3. A
4. G
5. T
6. G

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📝 Final Answer: Labeling the Bases

If we're filling in the blanks on the diagram, here’s how the horizontal rungs should be labeled:

| Top Strand | Bottom Strand |
|------------|---------------|
| A | T |
| G | C |
| T | A |
| C | G |
| A | T |
| C | G |

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💡 Explanation

This structure reflects the double helix model of DNA proposed by Watson and Crick. The sugar-phosphate backbones form the sides of the ladder, while the nitrogenous bases form the rungs. The specific pairing ensures genetic information is accurately copied during cell division.

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✔ Summary

To complete the diagram:
- Match each base on one strand with its complement:
- A → T
- T → A
- G → C
- C → G
- Fill in the missing base names on the horizontal lines accordingly.

Let me know if you'd like a visual version or help labeling specific parts!