Curio Cabinet

Conventional wisdom has long had it that dogs age seven times faster than humans—until now. In a recent study conducted at the University of California San Diego's school of medicine, researchers proved that it isn't that simple. In fact, a one-year-old pup is actually comparable to a 30-year-old human. Well, sort of. The researchers discovered that and more by tracking epigenetic changes to DNA in humans and 100 dogs as they aged. In particular, the scientists focused on methyl groups. These molecules play several functions involved with bodily development and synaptic growth in the brain. So by tracking how methyl groups accumulate rapidly in genomes, the researchers were able to compare and contrast the adolescent growth spurts dogs and humans experience. It turns out dogs reach the age of "30" within the span of one year. By four, canines are roughly 54 in "human years." Meanwhile, a 14-year-old dog is comparable to a septuagenarian human. But this brings into question the philosophical question of what age means in a developmental context. The study found that although one-year-old dogs were on par with 30-year-old humans, those dogs were still maturing hormonally, which isn't the case with humans at that age. In other words, comparing the developmental ages of two species isn't as easy as juxtaposing one factor. Regardless, the next time the puppy won't stop acting up, remind them they need to act like a 30-year-old adult should!
 

Image credit & copyright: Antonio Diaz/Getty Images/iStockphoto
 

The world's most famous sheep has us seeing double.

It takes a lot for a common domestic sheep to make international headlines! Then again, there was nothing common about the way that Dolly entered the world on July 5, 1996. Dolly was a clone: an artificially-created, genetically-identical reproduction of an existing organism. Although Dolly wasn't the first-ever clone ever, she was the first created from the cell of an adult animal—which, let's just say, caused an uproar.  

The term "clone" was coined in 1903 by Herbert J. Webber, a plant physiologist. He derived it from the Greek word "klon", or "twig", using it to describe the process of creating new plants from cuttings. Later, in 1938, embryologist Hans Spemann proposed the idea of replacing the nucleus of an egg cell with that of a different egg cell, creating a new organism. In 1958, developmental biologist John B. Gurdon built on Spemann's method to clone frogs, as did biologists Karl Illmenese and Peter Hope, who produced the world's first cloned mammal, a mouse, in 1981.  

In 1995, biologists Keith Campbell and Bill Ritchie of the Roslin Institute successfully created two sheep clones from embryonic cells. This progress excited fellow Roslin Institute scientist Ian Wilmut, and opened the door for a happy accident which would become Dolly the sheep. While trying to make more sheep clones from embryonic cells, scientists on Wilmut's team used some adult cells as a control group. The scientists took cells from the mammary tissue of a six-year-old Finn Dorset white sheep and injected them into unfertilized egg cells from a Scottish Blackface ewe, which had had their nuclei removed. Using electrical impulses, the scientists fused the eggs. They didn't expect any of the adult cells to successfully develop into an embryo. But when one did, they transplanted it into the uterus of a different Scottish Blackface ewe.  

Out of 277 cell fusions created by scientists, 29 embryos were implanted into 13 surrogate sheep, and just one developed fully. That one lamb, named Dolly, was born with a telltale white face—proof that she was a Finn Dorset white sheep, despite the Scottish Blackface ewe that birthed her. Dolly didn't receive her famous name, nor was the media informed of her birth, for several months after she was born. So where did her name come from? None other than famous country singer Dolly Parton. As scientist Ian Wilmut (rather unscientifically) put it, "Dolly is derived from a mammary gland cell and we couldn't think of a more impressive pair of glands than Dolly Parton's."  

Once the Roslin Institute announced Dolly's birth in February 1997, the sheep became a household name. The original purpose of the Institute's cloning experiments was to find out whether medicines could be produced from the milk of farm animals. But the main media buzz surrounding Dolly was the role of science in everyday life. If sheep could be cloned, why not humans? Could this technology allow entire human organs to be grown, for transplantees? What about cloned animal meat? In 2001, The United States passed a wide-ranging bill banning all forms of human cloning, even "therapeutic cloning," in which cells are harvested from embryos to treat disease. The law was passed largely due to the international conversation about cloning that surrounded Dolly.  

Dolly managed to live a normal life with other sheep at the Roslin Institute, despite the hubbub she caused. She even gave birth to several lambs, proving that clones could reproduce. At the age of six, Dolly contracted a virus which caused her to develop lung tumors. There was no evidence that Dolly's condition was linked to her being a clone. In 2003, she was euthanized to prevent suffering. Dolly's legacy lives on in the form of the cloning technology she helped popularize. More mammals have been cloned since Dolly's death, including pigs, cats, and dogs, ensuring that the world will continue seeing double for a long time!