A DNA paternity test will show a less than 1% probability if the tested man is not the actual father.

Like counting how often a word is repeated in a sentence, forensic scientists can identify people by tallying how often short segments of genetic information repeat in specific parts of a person's DNA—a set of numbers that varies from person to person. (Paywall may apply.)

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.

Extremely rarely, there can be twins with different dads—but fewer than 20 such cases are documented worldwide

The non-identical twins, who would also be half-siblings, result from a rare biological phenomenon called heteropaternal superfecundation. Britain's first known twins with different dads, featured in this article, learned of each other's existence in recent years, when they were both 45. They discovered each other after taking DNA tests from Ancestry, a genealogy company.

Many of the new prenatal genetic tests for rare genetic conditions are inaccurate

Established screening tests for Down syndrome in utero are reliable and accurate. But a New York Times investigation into expanded prenatal genetic tests for very rare diseases—much rarer than Down syndrome—found that more than 80 percent of the positive test results turned out to be wrong based on follow-up testing. These expanded tests for rare diseases are performed from a blood draw at 10 weeks of pregnancy and aim to detect chromosomal abnormalities linked to rare diseases. Companies that offer these controversial tests counter that it's only a screening test—not a diagnosis—picking up true positives and noting that patients can and should be counseled about what the findings mean. (Some users may encounter a paywall.)

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.

Why your dog’s DNA isn’t destiny

DNA tests tell people about their pet’s breed and attempt to predict things about its behavior and health. But for all that these tests might provide some interesting results, they need to be taken with caution. Here's a look at what we can and can't learn from our pets' DNA.

Only about 0.0001% of sperm, on average, successfully reach the uterine cavity

We've evolved to make pregnancy a complex and difficult process. From the initial development of the blastocyst, to the energy and nutrients needed to grow a new human, our bodies are both fighting and supporting fetal development.

The ancient Egyptians developed the first pregnancy test—and scientists tested it in the 1960s and discovered it was accurate about 70% of the time.

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.

The Golden State killer case spotlights how genetic testing can affect your—and your relatives'—privacy

Police managed to use consumer DNA test results to close a case 32 years after a killer was believed to have committed at least 12 murders and 50 rapes. Their "smoking gun": They compared a DNA sample from the crime scene to genetic data relatives had shared on an open-source genealogy database. The suspect was caught after investigators explored family trees on this database and connected the dots from over 100 distant relatives who had some percentage of DNA that matched the killer. (Some users may encounter a paywall.)

A man’s genes can predict his hairline

There’s actually some truth to the idea that you should look at your mother’s father. But genetic research tells us that the full picture is somewhat more complicated. An interesting read on how to use genetics to figure out if you'll go bald (with illustrations).

Mitochondrial DNA swapping can occur before or after fertilization

Mitochondrial replacement therapy can be conducted with four different techniques, with varying genetic material transferred depending on the approach. Maternal spindle transfer, one common method, involves transplanting the nuclear DNA from a mother into an unfertilized egg from a donor. The donor egg is then fertilized and implanted into the mother's uterus using in vitro fertilization. Another major approach, pronuclear transfer, does the genetic swapping after the mother's egg has already been fertilized. This order of operations may be uncomfortable for some individuals, but the success rate with this technique is higher.

Salvador Dalí’s remains were exhumed for a paternity test

Years after Dalí’s death in 1989, fortune teller Pilar Abel filed a suit claiming she was the child of an affair Dalí had with her mother. In 2017, Dalí’s body was exhumed for testing. Dalí was not the father, but the artist’s mustache remained intact decades after his passing.

How uploading your consumer genetic testing could lead to a distant relative's arrest

This podcast includes a discussion about how law enforcement can compare DNA samples from a crime scene against voluntarily uploaded DNA on consumer genealogy databases to close cases. Investigators can and have cross-referenced a suspect's crime scene DNA with that of a suspect's relatives who happened to have chosen to upload their genetic information to an open-source genealogy database.

The 4% DNA difference between humans and chimps

On the genetic level, we're not all that different from chimps. But those small differences in DNA can have huge effects. This 11-minute video digs in to the topic.

A new AI-assisted reproductive technique is finding 'hidden' sperm cells for those with very low sperm counts

Known as the Star system—for Sperm Track and Recovery—it uses artificial intelligence to help identify and locate "hidden" sperm in men with a rare infertility condition called azoospermia. The condition affects about 1% of men, and these individuals have sperm counts low enough that the individual spermatozoa in their ejaculate may be undetectable. In late 2025, the first baby was born after the child's parents used this assistive technique to locate sperm.

Modern pregnancy tests detect a specific hormone in a woman's urine or blood

They pick up human chorionic gonadotropin, in either blood or urine. The hormone is produced by a woman's reproductive tissues during pregnancy.

Modern genetic testing stems from a 1950s discovery about the cause of Down syndrome.

Read the 1963 study testing out an ancient Egyptian pregnancy urine test

The study sought to test out the ancient Egyptian approach of having a woman urinate on barley and wheat seeds to ascertain pregnancy status. Surprisingly, the research concluded that pregnant women's urine did promote growth of cereal grains the majority of the time; nonpregnant women's urine did not. Unfortunately, the sex of the child could not be accurately predicted based on which crop grew.

Pregnancy at older ages increases the chances of fetal abnormalities

Chromosomal irregularities are more likely at older maternal ages so genetic testing for a fetus of mothers-to-be at age 35 and older is often recommended. Conditions that can be screened for in utero include cystic fibrosis, Tay-Sachs disease, sickle cell disease, Down syndrome, spina bifida, Duchenne muscular dystrophy, and more.

US regulators have approved an at-home genetic test looking for BRCA gene mutations

The direct-to-consumer genetic test, approved by US regulators in 2018, examines 3 out of the more than 1,000 known breast cancer-linked genetic mutations. It looks for genetic variations that can increase risk for breast, ovarian, and other cancers. These mutations are most commonly found among Jewish people with Eastern European ancestry.

3-parent IVF removes most—but not all—faulty mitochondria

The process scoops out about 99% of the mother's mitochondrial DNA—replacing it with that of a donor woman—but because that roughly 1% is still in the system there is still a small chance of disease for the resulting child or future generations. (Some users may encounter a paywall.)

Silicon Valley startups Orchid, Nucleus, and Genomic Prediction are selling so-called polygenic tests for prospective parents

These tests claim to show how at-risk a hypothetical baby would be for genetic syndromes. The newfound industry has prompted ethical and medical debates, with critics questioning their accuracy and highlighting the potential problems behind pursuing the perfect baby.

What percent Neanderthal are you?

Many of us carry around 2% Neanderthal DNA in our genes. Museum human evolution expert Prof. Chris Stringer discusses why and what it means.

Genomic sequencing is the process of determining the order of nucleotides that make up an organism's genetic information and can be done in about 24 hours or less for human DNA.

You're probably 2% Neanderthal

Scientists examining the evolutionary history recorded within our DNA are uncovering the global human story in greater detail. Watch the film to discover what percent Neanderthal you may be.

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.

There was a backlog of at least 25,000 untested rape kits in 2022, according to data submitted from 30 states and Washington, DC.

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 pregnancy test industry is worth roughly $769M

The inventor of the at-home pregnancy test, Margaret Crane, largely hasn't taken credit for her invention until recently.

About 70% of the Human Genome Project's reference genome came from one donor

Volunteers who donated blood to the Human Genome Project consented to using no more than 10% of their DNA, raising questions about the project's legality. Listen to how pressure from a private competitor may have driven officials to ignore ethical standards.

The average person can only detect someone is lying 54% of the time

Scientific research shows that avoiding eye contact or fidgeting—behaviors typically associated with deception—do not reliably communicate dishonesty. Polygraph tests are considered "junk science," with the best means of detection relying on evidence and contradictions.

Alternatives to polygraphs, which correctly identify innocent people only 57% of the time

Lie detector polygraphs have been standard in law enforcement for a century despite being based in unproven science. Researchers are exploring brain-scanning and eye-tracking alternatives, though some suggest there's no reliable lie-detection process at all.

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.

Research shows that, on average, humans correctly spot liars about half of the time

Polygraph tests, also known as lie detectors, are better at detecting lies than people, but they still aren't allowed in most courtrooms. That's in part because of mixed signals. For example, spikes in heart rate can be explained by the stress a person feels during interrogation rather than by their own deception. As a result, polygraph tests are prone to false accusations. Results are also unreliable when participants actually believe their lies, examiners have biases, and tricks are employed to help test-takers relax.