What Is DNA?
DNA stands for deoxyribonucleic acid. It is the instruction book inside every living cell. DNA tells our bodies how to grow, what color our eyes are, and how our cells work. Although DNA is very small, its discovery has had a huge effect on science and medicine.
Early Clues
The story begins in 1869, when a Swiss scientist named Friedrich Miescher found a new substance inside cells. He called it “nuclein,” because it came from the nucleus, or center, of the cell. At that time, no one knew its purpose. Later, in the 1940s, researcher Oswald Avery and his colleagues showed that this substance—DNA—carries genes, the units of heredity passed from parents to children.
Seeing the Shape
Scientists then wanted to know the structure of DNA. In the early 1950s, Rosalind Franklin used a method called X‑ray diffraction to take very clear images of DNA. One of her images, known as Photo 51, revealed a repeating pattern that suggested a spiral shape. Her careful work provided essential evidence, even though she was not widely recognized at the time.
The Double Helix
In 1953, James Watson and Francis Crick, building on data from Franklin and Maurice Wilkins, proposed the famous double helix model. Imagine a twisted ladder: the two sides are chains of sugar and phosphate, and the steps are pairs of chemical bases—A with T, and C with G. This simple, beautiful model explained how DNA can copy itself and pass information from one generation to the next.
Why It Matters
The discovery of DNA’s structure opened the door to modern biology. Scientists learned how genes work and how changes in DNA can cause disease. New fields grew quickly, including genetics and biotechnology. Today, doctors can test for genetic conditions, and researchers can design new treatments by studying our DNA.
From Discovery to Today
In the late 20th century, international teams began the Human Genome Project. Their goal was to map all the genes in human DNA. By the early 2000s, they produced a first complete map. This work helps doctors find the causes of illnesses and supports the development of personalized medicine—treatments designed for a person’s unique genetic makeup.
Looking Ahead
Understanding DNA also raises important ethical questions. How should we use genetic information? Who should have access to it? These discussions continue today. Still, the discovery of DNA remains one of the most exciting stories in science: it shows how many people, over many years, can work together to solve a great mystery of life.
Vocabulary List
Tap the speaker to hear each word.
- DNA — The molecule that carries genetic information.
- gene — A unit of heredity that influences traits.
- structure — The way parts are arranged or built.
- double helix — A twisted‑ladder shape of DNA.
- mutation — A change in DNA.
- X-ray diffraction — A method to image tiny structures like DNA.
- heredity — The passing of traits from parents to children.
- biotechnology — Using living systems to make products or solve problems.
- ethics — Ideas about what is right and wrong.
- genome — All the genetic material in an organism.
Comprehension Questions
- What does DNA do in our cells?
- Who first found DNA and what did he call it?
- How did Rosalind Franklin help scientists understand DNA?
- Describe the double helix using the ladder comparison.
- Why was the discovery of DNA’s structure important for medicine?
- What was the goal of the Human Genome Project?
- Name one ethical question that comes from studying DNA.