## **Core Concept**
The human genome is made up of more than 3 billion **base pairs** of **DNA**, which are organized into 23 pairs of chromosomes. The base pairs are composed of **nucleotides**, each containing a **phosphate group**, a **sugar molecule** (deoxyribose), and one of four **nitrogenous bases**: **adenine (A)**, **guanine (G)**, **cytosine (C)**, and **thymine (T)**.

## **Why the Correct Answer is Right**
The correct number of base pairs in the human genome is approximately **3.2 billion**. This was determined through the **Human Genome Project**, which was an international research effort that aimed to sequence and map the entire human genome. The project was completed in 2003, and it revealed that the human genome consists of more than **3.1 billion base pairs** of DNA.

## **Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it underestimates the actual number of base pairs in the human genome.
* **Option B:** This option is incorrect because, although closer, it still does not accurately represent the number of base pairs in the human genome.
* **Option D:** This option is incorrect because it overestimates the actual number of base pairs in the human genome.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the human genome contains approximately **3.2 billion base pairs** of DNA, which are encoded with around **20,000-25,000 protein-coding genes**. Understanding the structure and content of the human genome is essential for appreciating the genetic basis of disease and the development of **genetic testing** and **gene therapy**.

## **Correct Answer:** . 3.2 billion