A LIBRARY OF DISCOVERIES
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Results 32
DNA evidence for different paternity
In 2020, researchers in Colombia described a case of fraternal twins in which one man had a 99.9999% probability of paternity for one twin but was excluded as the father of the other. The team examined autosomal and Y-chromosome STR markers; 14 of 17 Y markers and 14 of 21 autosomal STR markers did …
Identical twins' DNA
…om one fertilized egg and usually have very similar inherited genomes. But DNA changes can arise as cells grow and divide, so some twins have mutations found in only one of them. Other people also share most of their DNA: the commonly cited estimate of about 99.9% similarity counts differences in in…
The echidna: a spiny, egg-laying mammal
Echidnas, together with platypuses, belong to the monotremes, mammals that lay eggs. Like other mammals, they feed their young milk, but they have no nipples: milk is secreted through pores on specialized milk patches of skin, where the young lick it up. Their spines are modified hairs and provide p…
The length of DNA in the human body
If the nuclear DNA from all cells in a human body were uncoiled and laid end to end, one published estimate gives about 6.2 billion kilometers—roughly 41 Earth-to-Sun distances, not a trip to Pluto and back. The result depends on the number of nucleated cells, ploidy, and which cell types are counte…
DNA stores genetic information—with caveats
DNA stores hereditary information in the cells of almost all organisms and helps pass on instructions that influence development and function. But “all life” is too broad: some viruses store their genomes in RNA, and viruses are not cellular organisms.
The Double-Helix Model of DNA
In 1953, James Watson and Francis Crick published a model of DNA as a double helix. They proposed that the molecule’s two strands twist around one another and that bases on the strands pair in a complementary way. This structure suggested how each strand could serve as a template for copying DNA. Th…
DNA and the Cell Nucleus
If the DNA from all 46 chromosomes in a typical diploid human nucleated cell were laid end to end, its combined length would be about two meters. Inside the cell, DNA is not a loose thread: it wraps around histone proteins to form nucleosomes and is further organized into chromatin and chromosomes. …
Digital data can be encoded in DNA
In 2012, researchers encoded a 5.27-megabit digital stream in synthetic DNA, including book text, images and a program, then read it by sequencing. “700 terabytes per gram” should not be presented as a fixed limit or the actual file size written in that experiment: capacity depends on encoding, redu…
Cloning Dolly the Sheep
…te mother, she would have had a black face. A clone is not a copy of every DNA molecule from the donor: mitochondrial DNA comes mainly from the egg. The 1997 paper also reported live lambs produced from adult mammary-gland, fetal, and embryonic cell populations.
Fact 1265 — Dalton and color vision
…t the cause was an unusual blue tint in the eye’s vitreous humor. In 1995, DNA analysis of his preserved eye showed that he had deuteranopia, a form of red-green color-vision deficiency.
The Human Past Before Writing
…arths and settlements, sediment layers, pollen, plant remains, and ancient DNA when it survives. Each type of evidence reveals only part of the picture, and preservation is uneven: materials decay, sites remain undiscovered, or finds cannot be interpreted with confidence. Our reconstruction of the h…
Genes, traits, and environment
…so affect gene activity through epigenetic mechanisms without changing the DNA sequence. The contributions vary by trait and cannot be reduced to a simple “genes or environment” split. [1–3]
How hemocyanin’s copper binds oxygen
…iennius salei, researchers determined its subunit sequences using RNA-copy DNA analysis, gel electrophoresis, and mass spectrometry.
A cloud in a museum hall
In the Nimbus series, Dutch artist Berndnaut Smilde creates short-lived clouds indoors. He adjusts temperature and humidity, releases fine water droplets and fog or smoke into the air, and a photographer captures the result before the cloud disperses within seconds. The photograph preserves the mome…
Where the compass began
The magnetic compass was developed in China. Early lodestone devices were used for geomancy and orientation; Chinese use of the compass specifically for maritime navigation is documented from around the 11th–12th centuries. A magnetic needle aligns with Earth’s local magnetic field, so it points tow…
the story about cleaning Madonna’s dressing room
…e team finished. Vanity Fair repeated his remarks about hair and traces of DNA, but he described the practice as protecting the singer and making her comfortable. There is no independent confirmation that this was a standing policy or that Madonna herself said fear of DNA theft was the reason; sensa…
The platypus lays eggs
The platypus is a mammal in the order Monotremata, which also includes echidnas. Female monotremes lay eggs, but, like other mammals, they produce milk to feed their young. Laying eggs does not make the platypus any less of a mammal: egg-laying is a distinctive trait of monotremes within the mammal …
Political crisis and Cornelis's imprisonment
…nged to a man aged 40–50 in 1672, although it was not possible to obtain a DNA profile.
The one-letter place name Å
Several settlements in Scandinavia are named Å, just one letter long. The name is not unique: Guinness World Records also lists the Swedish place Y and France’s River E. In Norwegian and Swedish place names, the word å means “river” or “stream.”
A sloth and its fur ecosystem
…l are well understood. In a 2023 study, researchers sequenced short fungal DNA markers from the fur of ten two-toed and ten three-toed sloths living at the same site. The fungal communities differed between the species; in this sample, host species explained the differences better than sex, age, or …