National DNA Day - DNA Facts & History

By Vera Shively and Katherine Kim, Lurie Children's Division of Genetics, Birth Defects and Metabolism

April 25th is DNA Day. In April 2003 the United States Congress approved the first National DNA Day. It celebrates the 50th anniversary of the discovery of the structure of DNA and the 2003 completion of the Human Genome Project. Today, DNA Day is recognized around the world. It is a great opportunity for everyone to learn more about DNA.

What Is DNA?

Deoxyribonucleic acid (DNA) is a very large molecule that carries the instructions for an organism. Organisms include plants, animals, fungi, microorganisms and people! Molecules are groups of atoms held together by chemical bonds. The information in DNA is stored as a chemical code comprised of four nucleotide bases: adenine (A), cytosine (C), guanine (G), and thymine (T). We can think of DNA's nucleotide bases as a four letter alphabet. A gene is a long string of DNA that has instructions for making a specific product that an organism needs to grow and function. Parents pass down genes (the DNA code) to their child.

Why Was the Discovery of DNA’s Structure So Important?

Scientists discovered DNA's three-dimensional structure to be a double helix, resembling a twisted ladder. Once scientists understood the structure of DNA, we were able to start unlocking the mysteries of genes. Each rung of the DNA ladder is made of a base pair. Recall the four nucleotide bases mentioned above, abbreviated by A, C, G and T. These bases pair (bind chemically) in a predictable way. An A always pairs with T, and C always pairs with G.

Since DNA is the basic unit of heredity, it has to be copied from one generation to the next. Understanding DNA structure revealed how this is possible. Notably, the base pairs that form the rungs of the DNA ladder can separate. Each half then acts as a template that allows a full copy of itself to be made. This simple mechanism is how genetic material is copied and passed to the next generation. It also provides a way to access and copy the instructions used to make products organisms need to grow and function.

The Human Genome Project

The Human Genome Project was an international effort to sequence and map the human genome. It took about 12 ½ years to complete. The genome of an organism is the complete set of its DNA instructions. The instructions are coded in a specific order of DNA’s four nucleotides (A’s, T’s, C’s and G’s). The order is called its sequence. DNA sequences are really long. The human genome contains about three billion base pairs and an estimated 30,000 genes.

The Human Genome Project also produced maps to show the locations of genes on chromosomes. Genes are tightly packaged into structures called chromosomes. Mapping where genes are on chromosomes helps scientists track inherited traits over generations. Besides things like eye color and dimples, inherited traits include those associated with genetic disorders. For example, genetic mapping was used to find the gene responsible for disorders such a cystic fibrosis and Duchenne muscular dystrophy. Identifying the gene or genes linked to a disorder furthers the understanding of the disorder and the development of new treatments.

Fun DNA Facts

  • Human beings may look different, but 99.9% of our DNA is the same.
  • Humans share about 50% of our genes with plants.
  • If one person’s DNA was unraveled and placed end to end, it would stretch from Pluto and back.

Check these links for more information about DNA and DNA Day activity ideas:

Learn more about Lurie Children's Division of Genetics, Birth Defects and Metabolism

Sign up for our Newsletter

Get health tips from our pediatric experts, news about ground-breaking research, and feel-good moments delivered right to your inbox.

Subscribe Now

Additional Blog Posts

Iron Deficiency Anemia in Kids

Iron deficiency is a common condition in kids that can affect their energy and growth. Our expert explains the signs, causes and treatments for kids with iron deficiency anemia. 

Read More

Bedwetting in Kids

Bedwetting is a common issue, affecting millions of children. Learn about causes, how to help your child stay dry at night and when to talk to a healthcare provider.

Read More

Measles in Kids: Symptoms & Prevention

The recent measles outbreak has many parents and caregivers concerned. Our experts share what you need to know about measles in kids.

Read More