Genes are the basic units of heredity

DNA carries the unique instructions that shape how each person grows and functions

The human genome contains over six billion DNA letters, organized into 46 chromosomes inherited from both parents. Genes—sections of DNA—serve as templates for making proteins, and variations in these sequences can affect how our bodies work or respond to the environment.

Only 2% of human DNA codes for proteins

The entire human genome contains about 20,000 protein-coding genes, with the rest having initially been categorized as "junk" DNA. However, research since 2003 suggests that this "dark genome" regulates how protein-coding genes are expressed in response to environmental factors encountered by cells.

Cells translate genetic information into proteins using RNA messengers

Genes are segments of DNA, each composed of a sequence of nitrogenous bases. Within the nucleus, these sequences are copied into a single strand of ribonucleic acid during transcription. This strand leaves the nucleus and is translated by ribosomes into a chain of amino acids that folds into a functional protein.

DNA's four-letter blueprint makes the variety of all living things possible

The proteins responsible for cellular functions and an organism's traits are built outside of a cell's nucleus from RNA—single-stranded molecules created by reading the information in DNA. DNA's double-stranded structure makes it more stable and allows RNA to be made from either of its complementary strands.

All humans share 99.9% of the same DNA

Of the 3 billion base pairs that make up the human genome—the complete set of genetic material for the species—the diversity of humans is the result of variations in about 3 million molecular bases. The closest nonhuman genetic match is the chimp, with 98.8% similar genetics.

Half of human DNA is inherited from each parent

Within most cells reside 23 pairs of chromosomes made of tightly wound DNA, and half of each pair is inherited from each parent. The 23rd pair consists of two X-shaped chromosomes, or one such chromosome paired with a Y chromosome, and determines biological sex.

Bacteria helped scientists realize that DNA was the hereditary molecule, not proteins

Until the mid-1900s, most scientists believed genes were made of proteins, which were known to act as enzymes, hormones, and other chemicals that mediated an organism's traits. The Avery-MacLeod-McCarty and that benign bacteria could be made lethal, where the inherited factor that caused bacterial transformation contained DNA.

Watch how DNA is packaged to a 10,000th of its original size in a cell

In humans, the 2-meter (6.56-foot) molecule wraps around spool-like proteins called histones, forming beads—nucleosomes—that fold up into fibers. These fibers—chromatin—form loops through folding that compress into larger fibers, which tightly coil together to form a chromosome.

Mitochondria—only inherited from mothers in most animals—have their own DNA

Mitochondrial DNA, or mtDNA, typically takes the shape of a circle and contains genes that code for proteins essential to the production of energy-containing molecules called ATP. When mitochondria fuse, the mixing of healthy and damaged mtDNA helps alleviate the effects of mutations that may have occurred during mitochondrial division or environmental interactions.

The history of the gene: an interactive timeline

Humans didn’t need modern technology to figure out that kids tend to look like their parents. But what did humans believe about genetics before we knew about DNA or cells in general? Explore this interactive timeline to see how philosophers and scientists throughout the ages tried to explain how traits are passed from generation to generation.

Where do genes come from?

There are many more genes on Earth today than when microbial life first spawned on the planet about four billion years ago. Many of these newer genes grew from genetic mutations, misprints that slowly drift from the original blueprint via cellular division. If these mutations drift far enough, they can establish a new family of genes, though this process can take well over a million years.

Common genetic disorders

As research continues, it's clear that disease and genetics go hand in hand. Here's a selection of 50 National Human Genome Research Institute (NHGRI) articles providing basic information on genetic, orphan, and rare diseases caused by mutations in DNA sequences, whether inherited from parents or brought about by outside factors.

What is a cell? A great quick overview.

YourGenome.org furnishes a collection of information on cells and how they work. Every body has trillions of cells, each serving a specific function: making proteins, processing chemicals, and creating energy. Every cell contains a genome, a set of instructions for the cell's function. Brush up on your cells for a better grasp on genetics.

What is genetics?

What is a genome, and how are traits passed from generation to generation? Learn how pea plants helped launch the study of genetics and how the field of genetics research has evolved over time.

All publicly available DNA sequences are available at GenBank

The National Institutes of Health's database stores comprehensive, annotated DNA sequences as part of the International Nucleotide Sequence Database Collaboration. It encourages unrestricted data access within the scientific community while allowing submitters to retain intellectual property rights over their data.

Nitrogenous bases connect like puzzle pieces due to their shape

There are four bases—adenine, thymine, cytosine, and guanine—which keep the two strands of DNA connected via chemical bonds between them. Connections between thymine and adenine require two hydrogen bonds, while those between cytosine and guanine need three hydrogen bonds. These differences in bond number prevent non-complementary pairings.

Ancestry testing matches DNA to known genetic variants found in specific ancestries

After a lab receives a person's sample, the DNA is separated into single strands, which are chemically cut into smaller fragments. The fragments are then fed into an array of variants of known origins, and technicians observe if a person's fragments bind to specific variants.

DNA cassette tapes could store 36,000 terabytes of data

By translating binary code into the base-pair code found in genetic sequences, researchers in China are storing digital data on DNA-coated tapes for compact, durable, and energy-efficient storage. The tapes use a blend of polyester and nylon with barcode patterns for data addressing.

In 2025, researchers in the UK began working on developing artificial DNA

The Synthetic Human Genome Project aims to one day construct human DNA, molecule by molecule, in the hopes of creating disease-resistant cells and synthetic chromosomes for study. However, critics warn it may be misused to create enhanced or modified humans.

Gene therapy treats a disease by editing its DNA source

This modification is typically performed by viruses, which are naturally skilled at entering cells but have their disease-causing component removed before delivery. Once inside, cells can use the inserted genetic material to produce more helpful proteins, fewer harmful ones, or create new proteins.

Genetic tests aren't always actionable, which is one reason genetic counselors are so vital

This podcast interview with a Harvard Medical School professor focused on cancer genetics and prevention discusses the specifics of genetic testing and insights and the challenges of processing the outcomes of the testing and what may be actionable—or not.

Cells are categorized by the presence of contained genetic material and other organelles

While prokaryotes contain one or more cells with free-floating genetic material in a region called the nucleoid, eukaryotes possess a nucleus specialized for DNA storage. Plant cells possess cell walls—a reinforced structure surrounding their membrane—made of cellulose, while fungal cell walls contain chitin. Animal cells have lysosomes housing enzymes that break down biomolecules. (Some readers may experience a paywall.)

Nature versus nurture: Are you the result of your genes or your environment?

Dr. Nancy Segal breaks down how research on twins has revealed just how much our genes influence our behavior and traits—but insists they aren't everything. Catch up on the latest in the nature versus nurture debate.

Sex determination isn’t all XX and XY

We’re generally taught that chromosomes determine an animal’s sex, but it is way more nuanced than that. Watch this 12-minute video to find out how.

Exercise changes your genes without changing your DNA

Physical activity can turn beneficial genes on and harmful genes off, without altering the underlying DNA code. This engaging article explains the epigenetic mechanisms that take place with exercise and ultimately result in improved metabolism, lower inflammation, and optimized brain function.

Visualize how CRISPR-Cas9—a type of immune system used by single-celled organisms to attack invasive viruses—targets and makes precise changes to a gene's DNA.

The first line of 'immortal' human cells, which can divide indefinitely and are used in scientific research, was nonconsensually taken from a Black woman.

Bone marrow (soft tissue found inside certain bones) generates roughly 500 billion new blood cells each day

Radioactive elements can introduce software errors because the ionizing radiation they produce can detach electrons from atoms, and computer code relies on the distribution of electrons.

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