How DNA works - an illustrated guide explaining the structure of DNA, base pairing, and its role in cell division and protein synthesis.

Actually, there is no explicit “problem” or “task” presented in the image you uploaded. Instead, the image is an educational infographic titled “How DNA works.”

It explains the structure and function of DNA in a simplified, visual way — perfect for learning or teaching basic genetics.

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✔ So what *can* we do?

Since no specific question was asked (like “What base pairs with C?” or “How many chromosomes are in a human cell nucleus?”), I’ll provide a comprehensive summary and explanation of the key concepts shown in the image — essentially solving the “task” of understanding how DNA works based on this diagram.

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## 🧬 Summary & Explanation: How DNA Works (Based on the Infographic)

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1. Discovery & Importance

- The defining moment for DNA was the discovery of its double helix structure in 1953 (by Watson and Crick, using Rosalind Franklin’s X-ray data).
- DNA is the genetic material that forms chromosomes inside the cell nucleus.

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2. Human Cell Nucleus

- Contains 46 chromosomes (23 from each parent).
- Chromosomes are tightly packed bundles of DNA.

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3. Chromosome → DNA

- When unraveled, a chromosome consists of double-stranded DNA.
- DNA is made up of four chemical bases:
- A = Adenine
- T = Thymine
- C = Cytosine
- G = Guanine

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4. Base Pairing Rules (Complementary Base Pairing)

This is the core of DNA structure and replication:
> “Where one strand has ‘A’, the other must have ‘T’; where one has ‘C’, the other must have ‘G’.”

- This is called complementary base pairing.
- A always pairs with T (via 2 hydrogen bonds).
- C always pairs with G (via 3 hydrogen bonds).

✔ This ensures accurate copying during replication.

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5. Genes

- Sections of DNA form genes.
- Genes contain instructions for making proteins, which are essential for:
- Growth
- Maintenance
- Function of the body

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6. Cell Division & DNA Replication

When a cell splits (during mitosis):

#### Step 1: DNA strands come apart
- The double helix “unzips” — the two strands separate.

#### Step 2: Spare bases are added
- Free-floating bases in the cell (A, T, C, G) match up with the exposed bases on each strand.
- Where there’s an A on the old strand, a T is added.
- Where there’s a C, a G is added — and so on.

#### Step 3: Two identical double helices form
- Each original strand becomes part of a new double helix.
- Result: Two identical DNA molecules, one for each new cell.

This process is called semi-conservative replication — each new DNA molecule has one old strand and one new strand.

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7. Double Helix Form

- After replication, the newly formed strands twist back into the iconic double helix shape.
- This maintains the stable, compact structure needed to fit DNA into the nucleus.

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## 💡 Key Takeaway:

DNA is like a biological instruction manual written in a 4-letter code (A, T, C, G). It replicates itself precisely during cell division so that every new cell gets an exact copy of the genetic instructions.

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## ❓If You Had a Specific Question…

If you meant to ask something like:
- “What base pairs with C?” → G
- “How many chromosomes in a human cell?” → 46
- “What happens when a cell splits?” → DNA unzips and copies itself
- “What are genes?” → Sections of DNA that code for proteins

…then now you have the answers!

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## 🎯 Final Answer (as if solving a “task”):

> The image explains how DNA stores genetic information as a double helix made of four bases (A, T, C, G), follows strict pairing rules (A-T, C-G), and replicates itself during cell division by separating strands and using spare bases to rebuild two identical copies — ensuring each new cell inherits complete genetic instructions.

Let me know if you’d like a quiz, worksheet, or deeper dive into any part! 🧬📚