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

Recombinant DNA technology turns microorganisms into protein factories

Genes for molecules such as insulin can be inserted into loops of bacterial DNA called plasmids and reinserted into bacteria. Once placed in fermentation tanks, these bacteria use the gene to produce these molecules, which are then harvested and purified for eventual use.

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.

Genes are the basic units of heredity

These segments of DNA—long molecules made of nucleotides that coil into chromosomes—code instructions for making specific proteins, which correspond to different traits. Approximately 98 to 99% of human DNA is non-coding, with functions beyond protein synthesis.

An estimated 1% of DNA mutations in bacteria can produce more dangerous strains

Researchers have developed a technique to monitor these mutations in real time. Using this technology, scientists found that mutations occur at a steady rate, with 1% leading to potentially deadly changes.

Changing a single letter in DNA can permanently alter an organism

Genetic mutations occur when cells replicate, which requires a copy of DNA to be created, and involve substituting, deleting, or inserting letters in a cell's genetic code. Mutations can be caused by normal cellular processes, chemical exposure (e.g., carcinogens), or radiation and may result in genetic disorders or genetic variations that drive evolution.

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.

RNA may have allowed life to exist before DNA

The emergence of living organisms from non-living matter—abiogenesis—requires both a molecule that encodes genetic information and proteins that perform biochemical processes. However, because DNA and protein depend on one another, some biologists theorize that RNA, which can both store information and perform functions, preceded both and originated life.

View a collection of historical documents about molecular biology's history

The collection features materials related to those involved in the discovery of DNA and provides historical context for the discoveries of RNA, various viruses, and important bioproteins. The items include photographs, business correspondence, manuscripts, and scientific instruments.

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.

The structure of DNA helices comes in three major varieties

The hereditary molecule can take the form of A-DNA, B-DNA, or Z-DNA based on environmental conditions such as ion concentration and humidity—a characteristic identified by Rosalind Franklin. A-DNA is the shortest and widest of the three, while Z-DNA is the longest and narrowest. B-DNA—the most common variety in living cells—is the intermediate.

Watson and Crick revealed DNA's double-helix structure using others' key findings

Their 1953 model, made from cardboard cutouts, explained how DNA stores genetic information through base pairing. Rather than experimenting and collecting their own data, they incorporated patterns and data from other scientists through trial and error.

Bacteria rapidly evolve (and share) new defenses against drugs they encounter

Unlike humans, bacteria rapidly make genetic changes in response to their environment, including creating defense against antibiotics. Furthermore, these defenses are passed on to their future generations and can even be shared with neighboring bacteria through horizontal gene transfer.

Glowing chemicals allow scientists to read DNA like a barcode

The process of determining the order of nitrogenous bases in DNA involves first cutting the DNA into fragments, which are duplicated multiple times using bacteria. Fluorescently labeled terminator bases are added to fragments, which are sorted by length and read via laser to reconstruct the sequence.

The discovery of the first extremophile and how it revolutionized DNA analysis

While investigating samples taken from within and around the hot springs at Yellowstone National Park, microbiologist Thomas Brock discovered Thermus aquaticus, a microorganism that thrived in hot water. It contained an enzyme called Taq polymerase, a critical molecule in polymerase chain reaction—a molecular photocopier that amplifies genetic signals to improve medical diagnostics.

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.

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.

Watch how proteins are created from DNA

When a DNA sequence—a gene—is activated, a copy of the activated portion is created in the form of RNA, a single-stranded version of DNA, in a process known as transcription. This RNA, called messenger RNA, leaves the nucleus and travels to a ribosome, a structure within a cell, which uses it to build a chain of organic compounds that fold into a protein.

Rosalind Franklin was the long-overlooked contributor to discovering DNA's structure

Though James Watson, Francis Crick, and Maurice Wilkins are credited with discovering the DNA double helix, it incorporated Rosalind Franklin's unpublished data. Photo 51, her famous DNA image, took more than 100 hours to produce and a year’s worth of analysis to interpret.

CRISPR-Cas systems act as genetic memory banks for defending bacterial cells

When viruses called phages inject DNA into bacteria, some bacterial species store bits of this DNA in their own genomes. This allows them to recognize and destroy the same virus if it attacks again.

X-ray data from Rosalind Franklin was key to discovering DNA’s double-helix structure

Although unpublished, the data reached James Watson and Francis Crick, who worked at another institution. Incorporating her data allowed them to validate their model of DNA, which they published without crediting her.

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.

Some organelles are believed to have once been independent cells

Mitochondria and chloroplasts, which are both responsible for energy production in cells, have DNA distinct from that of their host cells and are surrounded by cellular membranes resembling those of bacteria. Through symbiogenesis, these and other specialized structures were absorbed into larger cells, forming the modern-day biological units.

Before discovering cells, life was believed to emerge suddenly from inorganic matter

Popularized by Aristotle in the 4th century BCE, spontaneous generation was used to explain phenomena like mice appearing in seemingly sealed grain storage. The invention of the compound microscope in the late 16th century led to the identification of cells as the basic unit of life, but it was not until 1855 that their origin from preexisting cells was established.

Genetic engineering has accelerated millennia of altering various crops' genes

Although farmers have long cross-bred crops to obtain plants with specific colors, sizes, and other characteristics, these processes took significant time. Today, genetic modification in agriculture involves scientists altering an organism's DNA for various purposes, including enhancing pathogen resistance, removing allergens, and delaying spoilage.

Beyond DNA, Franklin's legacy extends into modern virology and steel production

While remembered for her critical but under-credited role in uncovering parameters for the structure of DNA, Rosalind Franklin made significant contributions across coal chemistry and virus structure. Her research helped improve fuel efficiency, wartime protective equipment, and foundational knowledge in molecular biology.

Bacteriophages—viruses that infect bacteria before multiplying within them—exist on Earth in numbers greater than all other living organisms combined.

Before Dawkins, other biologists proposed the power of mutating ideas

Nobel Prize winner Jacques Monod proposed, “Ideas have retained some of the properties of organisms. Like them, they tend to perpetuate their structure and to breed; they too can fuse, recombine, segregate their content; indeed they too can evolve, and in this evolution selection must surely play an important role.”

Nature simultaneously published three papers on DNA—only the first made history

Papers by Watson and Crick, Wilkins, and Franklin were fast-tracked without peer review, and their order was arranged between lab heads and editors. Franklin's appeared last, making her paper read as though supporting Watson and Crick—because they'd already incorporated her data before it was published.

Gene therapy treats a disease by editing the disease's underlying DNA, replacing it with a functional variant.

See the history of DNA sequencing

DNA sequencing evolved from manual methods to automated, high-throughput technologies. The Human Genome Project was possible in the first generation of gene sequencing technology with the "chain termination method," which won developer Fredrick Sanger a Nobel Prize.

The woman erased from the DNA breakthrough

Rosalind Franklin captured “Photo 51,” the key to DNA’s double helix. Her data, shared without her knowledge, helped Watson and Crick win a Nobel. She never got the prize, but today, her role in unlocking life’s blueprint is finally recognized.

Storing data in DNA requires converting binary code into DNA's four-base system

Researchers have suggested that DNA's ability to form compact, dense structures justifies investigating its use for long-term, safe data archiving. This system could fit all of the world's data in a single shoebox, though processing each bit into a nucleotide base takes 2 minutes, as of 2024.

Gut bacteria are evolving and can acquire as many as 100 new genes per year, on average.

The history of germ theory, which explains that illnesses are caused by microorganisms

For centuries, the miasma theory, which held that illnesses were caused by clouds of "bad air" produced by decaying organic matter, was the accepted explanation for the spread of disease. The development of microscopes and the subsequent technology to isolate bacteria and test disease spread in mice greatly contributed to contagionists overturning miasmatists.

Strands of DNA can act as biochemical Velcro and fasten two molecules together because the complementary bases that make up DNA strands bond together consistently.

CRISPR-Cas9 enables precise genome editing using a simple RNA-guided system

Jennifer Doudna's research uncovered how bacteria use the tool as an immune defense by cutting viral DNA. She and Emmanuelle Charpentier received the 2020 Nobel Prize in chemistry for showing how this mechanism could be engineered to target and edit genes in living cells.

Watch how Sanger sequencing kickstarted the first generation of DNA sequencing

Sanger sequencing is a foundational DNA sequencing technology developed in 1977. The Nobel Prize-winning discovery uses fluorescent dyes at the end of DNA chains, which are sorted by length through electrophoresis, to determine the order of nucleotide bases.

Lyme disease-causing bacteria predate any suspected biological weapons testing

Borrelia bacteria existed long before any US biological weapons program—or human presence in North America. One study comparing genomes of the bacteria behind Lyme disease collected samples of the bacteria over three decades and calculated that the bacterium has been in North America longer than humans, at least 60,000 years. Other work found related bacteria preserved in amber from millions of years ago.

Learn how chloroplasts—the photosynthesis factories—may have once been independent cells

Possessing DNA of their own that differs from that of their host cell and surrounded by cellular membranes like those observed in bacteria, chloroplasts are believed to have evolved from a cyanobacterial cell. The endosymbiotic theory explains that these organelles were absorbed into larger cells, leading to the photosynthetic cells seen today.

Synthetic biology transforms cells into custom DNA foundries

At companies like Ginkgo Bioworks, researchers are reprogramming cells to act as workshops that can create custom molecules, such as medicines and fertilizers, by stitching together DNA sequences—often in novel combinations—before inserting them into an organism's genome.

Despite privacy risks, scientists are using DNA in the air to assess ecosystem health

While DNA in soil and water samples has long been used for such analyses, airborne DNA is being incorporated into such efforts to monitor individual species abundance, detect invasive species, measure biodiversity, and determine the success of conservation actions. Future work may include detecting attacks from biological weapons.

See a timeline of landmark discoveries in the field of genetics to gain a better understanding of more than a century of advances.

Around 5 million of our 3 billion DNA letters differ between individuals

Genetic testing examines gene variants to help explain disease symptoms. It explores how genetic differences between individuals can be used to understand risks of developing diseases like Huntington's Disease or passing variants linked to disease onto offspring.

Genetic engineering will change everything forever

Designer babies, the end of diseases, genetically modified humans that never age. Outrageous things that used to be science fiction are suddenly becoming reality. As scientists increasingly understand how specific genes cause disease, the possibility of engineering our genes to not only "fix" problems but enhance our natural ability grows.

Biologist Richard Dawkins coined the term 'meme'

His 1976 book "The Selfish Gene" proposed that units of culture could be replicated, passed on, and evolve as they were transmitted, similar to human genes. He called this unit a "meme," to be pronounced like "cream."

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.

Watson's book was described as misleading when detailing Franklin's role in DNA

Despite working together to win the Nobel Prize for their discovery of the structure of DNA, Francis Crick and Maurice Wilkins objected to the publication of James Watson's account of DNA's discovery. Those involved describe how he villainized Rosalind Franklin and downplayed her work.

Model organisms like yeast, mice, and flies help scientists decode the human body

Some species are used to quickly study the effects of human diseases and treatments because they are short-lived and have similar systems to those found in humans. Bacteria, like E. coli, have been used as human proxies given their rapid growth and ease of genetic manipulability.

Research on bacterial cultures used in yogurt production led to CRISPR's discovery

Scientists learned it was a microbial immune system that could be repurposed to protect dairy cultures from viruses. Today, nearly all yogurt is made with CRISPRized bacteria, as are genetically modified crops like herbicide-resistant corn, wheat, and soy.

Exercise can change your genes without changing your DNA.