Twins: Identical, Mirror Images, Fraternal and Chimeras

Cloning is not a human invention; nature has been creating clones for millions of years, among all organisms including humans. Nature’s clones, identical twins, are born in approximately 1 / 1000 births. Identical twins come in two varieties: identical and mirror images. Both share 100% of their DNA and but in mirror image twins, small differences are ‘reflected’. Examples include skin variations such moles, dental patterns, hairlines and handedness.

The development of a truly identical twins versus mirror image twins comes down to timing. A single sperm will fertilize a single egg and begins development by splitting into more cells. If this group of cells, now called blastocyst splits into two separate parts in the first 9-12 days, identical twins will be born. But if the split occurs after that, they will be mirror-images of each other.

Fraternal twins are an entirely different matter. Fraternal twins are no more identical than any other sibling pair and are the result of two separate sperm fertilizing two separate eggs. This is can occur naturally, the result of the mother releasing more than one egg at ovulation. It may also be the result of medical intervention as many women take fertility drugs to improve their chances of conception. There is also a hereditary link as the incidence of fraternal twins do occur more often within a family.

Many people have seen the popular American television show CSI (Crime Scene Investigators) and may recall the episode with the Chimera, a man who had two sets of DNA. This phenomenon occurs when the blastocysts of developing fraternal twins fuse, resulting in a single individual with two sets of DNA. This condition usually results in a fully functional individual and is not detected unless a clear abnormality prompts testing. Though it has been considered a rare condition, it is found to be more common than originally thought in a variety of animals, including humans. And the condition is more common among children conceived through in vitro fertilization than naturally.

By the way, you can read about the amazing birth of identical quadruplets from my hometown, Calgary, Canada here.

Happy Earth Day!

I’m sorry I’m a day behind! I hope that this weekend you were all able to enjoy some good weather and celebrate Earth Day 2007.

I’m not much for New Year’s resolutions but every year on Earth Day I try and make a change in my life that (however small) that will lower my impact on the environment. I have along ways to go towards a green lifestyle. Though I recycle and reuse my grocery bags I still do many, many other things that could be improved upon.

So for this year’s effort I will try to buy more local produce. I love exotic fruits and other foods and while I don’t plan on cutting these out of my diet entirely, I plan to have more seasonal meals and to try to appreciate the variety in which local foods can be prepared. Another advantage to buying locally is that it is often a cheaper option and you can buy directly from farmers and green grocers.

Here are 20 EASY ideas on how to contribute. All it takes is a little imagination and dedication. If you decide to make a change today, please leave a comment! Thank you, Sarda

Reduce, Reuse and Recycle
-Use plastic containers instead of cling wrap and aluminum foil
-Take your own bags to the grocery store
-Recycle where facilities exist
-Hold a garage sale
-Shop in used bookstores

Home, Office & Garden
-Turn the light off when you leave a room
-Use energy saving lightbulbs
-Use half as much washing powder
-But eco-friendly washing products (eg. Ecover)
-Purchase bleach free, recycled kitchen roll or use washable tea towels
-Use cloth napkins
-Put a ‘No Junk Mail’ sticker on your post box
-Buy organic
-Buy less meat, more fruits and vegetables
-Buy local
-Start a compost heap
-Use both sides of paper
-Bike, walk, carpool or use public transport to get to work.
-Pass read magazines to friends or give them to the doctor’s office

Holidays
-Personalize Christmas by being crafty and making new cards from old ones

Feathered Dinosaurs

A reader sent me this cartoon. Pollen has been found in high concentration with some Neanderthal bodies suggesting they buried their dead with flowers. But what about before flowering plants evolved?

Happy 100!

Well I have just posted my 100th post. Thanks to my regular readers and welcome to the new ones. I hope I am doing something right, I was recently awarded the Thinking Blogger Award by Oreneta, a Canadian sailor aground in Catalonia, Spain, thank you Oreneta! Now I will nominate five bloggers who make me think. I decided not to include science-related blogs which I have to admit are the majority of what I read, but rather consider five blogs which I make me think outside of my box.

The Domestic Minx has a deliciously dysfunctional diary about domestic living.

Ok, I said I wasn’t going to post a science blog, but this one is really good and completely out my realm of expertise. The (recently launched) All About Forensic Science blog explores anything and everything to do with forensic science.

Cucina Povera, which has a million great recipes for sustainable, organic living.

Wild in London is an excellent blog about the wildlife that can be found in one of the world’s largest cities.

and Clubbing Baby Seals... an interesting blog about the weird world around us and someone of the weirder products we can buy.

Tyrannosaurus Forelimbs Revisited

Earlier in the week, I posted some theories regarding the function of T. rex’s diminutive arms. I just thought I would add some recent research before I closed the topic:

Matt Smith (Museum of the Rockies) and Ken Carpenter (Denver Museum of Natural History) began examining the wrist, hand and finger bones of the T. rex forelimb and used wax to hold the bone joints together. This led them to figure out that the forelimb's two claws have an unusual feature: unlike the opposable human thumb and forefinger combo, which can grasp objects, the two dinosaur claws face away from each other like the barbs of a fishing hook.

What does this mean? Perhaps these claws embedded themselves into the prey’s flesh and immobilized it while T. rex used his jaws to finish the job. .

Matt Smith says, "People had been looking at [forelimb] function based on proportionate size. I don't think that's appropriate."

Sneezing in the Sun

After eight years and I am still learning new things my husband: we were walking down the street when the clouds parted, revealing a bright sun and he consequently sneezed! And now I realize that this phenomenon affects a significant number of other people I know. So in case you were ever wondering why looking at the sun on a bright day makes you sneeze here is the answer:

When a nerve cell is stimulated it passes on a chemical / electrical message to the next nerve cell in the chain. However, if it is a very strong message, this might also leak out and stimulate nearby nerve cells. So, when you look at the sun or a bright light, your eyes (and their nerves) suddenly have a lot of very strong information to pass to the brain. In addition to passing on their message, they also 'leak' a bit. Part of the path for the optic nerves (from your eyes) happens to be close to your sneeze reflex and so it can be triggered by accident.
-This text was originally contributed by David Hone on Ask a Biologist

Anecdotal evidence also seems to indicate that this unusual reflex has a genetic link, so may be common among members of the same family. This is confirmed by R. Eccles of the Common Cold and Nasal Research Group who says that this phenomenon (which he terms the ‘photic sneeze’) affects between 18-35% of the population. And that the photic sneeze is a well known hazard to fighter pilots when they turn towards the sun or are exposed to flares from anti-aircraft fire.

Shark Cartoons

Check out One Whale, home to 137 hilarious shark, whale and marine cartoons by Australian cartoonist Phil Watson.

Why do Great White Sharks always have a big bloody gape?

Something has been bothering me the last while. I can’t figure out why Great White Sharks are always depicted as having a big bloody gape? I have researched it a bit but have not come up with any good information. As it I see it though, there are three distinct possibilities:

1. The big bloody gape is a fallacy propagated by Hollywood
2. Blood is leftover from a kill
3. The blood is their own

There are few points to be noted about each possibility:

1. Purusing some stock photography (seen below) it seems that there a a mix of shark pictures, with and without bloody mouths. And of course, this may be subject to a photographer’s bias.

2. If the blood is indeed from a kill, why would it stain so long and not simply wash away? Also, it should be noted that Great Whites don't eat that often.

3. If the blood is their own, why doesn’t it attract other sharks?

If you have comments on this topic, please let me know, I would like to solve this mystery!

The Science of Superheros

Thanks to Eva of Easternblot for posting about some great websites on the science of superheros. If you’re a comic book nut but haven’t checked them out:
BBC’s has a great website on superhero science, profiling Spider-Man, Wonder Woman, Daredevil, Superman, The Incredible Hulk, and the X-men.

Ubergeeks will like Jim Kakalios’ book, The Physics of Superheroes and the Comic Book Periodic Table of the Elements (start with Oxygen on this one:)

BC creator dies while drawing last cartoon

Cartoonist Johnny Hart, who won awards for his comic strips, BC and The Wizard of Id, has died of a stroke at the age of 76.

BC, which depicted a world populated by cavemen and dinosaurs, first appeared in newspapers in 1958. The Wizard of Id was a political satire based in a run-down kingdom ruled by a diminutive and tyrannical monarch.

Johnny Hart’s comics reached over 100 million people. He died at his storyboard, doing what he loved best.

In the News: Ancient Humans, Great Pyramids and an Antarctic Amphibian

Mystery of the great pyramids solved
Original Publication: Dassault Systems
Popular News site: CBC

Ancient human fossil from China collides with ‘Out of Africa' theory
Original Publication: PNAS
Popular News site: BBC

Antarctic amphibian
Original Publication: JVP
A synopsis of the original article will be published on this blog later today.

Survival of the fittest: GM malaria-resistant mosquitoes out compete diseased relatives

A team of researchers announced today that they have genetically modified a species of mosquito resistant to the malaria Plasmodium parasite. And that these GM mosquitoes out compete their relatives because the infected mosquitoes suffer from effects of the disease. Experiments showed that from a population of equal proportions, nine generations after the insects fed off of malaria-infected mice, 70% of the bugs were the malaria-resistant type. This picture shows a GM mosquito, whose eyes glow green because of a second modified gene for green fluorescent protein (GFP).

I have strong beliefs about the genetic modification of foodstuffs because 1) we are casually tinkering with genomes nature spent millions of years fine-tuning - what makes us think we know what we are doing? Some times science has unexpected consequences. And 2) The desirability of ‘superior’ crops and livestock produced through selective breeding and genetic modification have created monocultural populations which are hypersensitive to environmental change and disease.

However, in the case of agriculture, most ‘tinkering’ is uneeded effort; in the case of malaria, a solution could prevent one million deaths each year. Will this disease be controlled by introducing GM insects into wild populations? Not in the near future, but may be someday.

Mauro T. Marrelli, Chaoyang Li, Jason L. Rasgon, and Marcelo Jacobs-Lorena. March 19, 2007. Transgenic malaria-resistant mosquitoes have a fitness advantage when feeding on Plasmodium-infected blood. Proceedings of the National Academy of Sciences.

Borneo and Sumatra clouded leopards are seperate species

Graeme Lloyd and Darren Naish post on molecular differentiation of two Clouded Leopard species on their blogs, This Life is a Fiction and Tetrapod Zoology.

Would the Real Indiana Jones Please Stand Up?

After my birthday blog on Roy Chapman Andrews, Darren Naish commented that it is a myth that Andrews inspired Indiana Jones. I admit that this is a commonly told anecdote and that George Lucas never specifically cited a person as his inspiration for the character. He apparently told Steven Spielberg when they first discussed the movie trilogy in 1977 that he had been inspired by movie serials from the 1940s and the 1950s. Though these serials may have taken their inspiration from the real-life adventures of Andrews, he had retired by 1942. Other possible candidates for Indian Jones include:

*Professor Hiram Bingham III, an American academic, explorer and politician who rediscovered and excavated the lost Incan city of Machu Picchu in 1911.

*Colonel Percy Harrison Fawcett a British archaeologist who disappeared in 1925 while searching for a lost city the Mato Grosso region of the Amazon jungle.

But perhaps the most interesting of ‘inspirations’ is religious archaeologist, Vendyl "Texas" Jones, who claims the fictional character was modeled after himself. He pointed out that by trimming his first name he could be ‘Endy Jones’ and claims his name made it into the movie by way of Randolph Fillmore, a science writer who attended one of his digs before writing the first draft of Raiders of the Lost Ark.

While Lucas and Spielberg remain generally tight lipped about their inspiration, Spielberg has adamantly denied that Vendyl Jones had any influence over the Indiana Jones character. Lucas says that Indiana is the name of his Alaskan Malamute and that originally he had planned on using the name Indiana Smith (after the fictional western movie character, Nevada Smith) but that Steven Spielberg changed it to Indiana Jones. Also, Randolph Fillmore was not involved in writing the first draft of movie And fortunately, Vendyl Jones has now stopped making his claim.

Albertaceratops nesmoi

News of a new horned dinosaur, Albertaceratops nesmoi made headlines earlier this month but I am a little behind! Though the dinosaur was discovered in 2001 and described in Ryan’s 2003 dissertation (as Medusaceratops) it has now been formally published. The generic name means ‘Alberta horned face’ and the specific name honours Cecil Nesmo, a rancher from Southern Alberta who aided the palaeontologists recovering the fossil.

The animal, known from a single complete skull and postcranial fragments, is from the middle Campanian (Upper Cretaceous) Oldman Formation of Alberta, Canada, and Judith River Formation of Montana, USA.

Distinctive features include: long brow horns a bony ridge over its nose two large outwardly-projecting hooks on its frill. Ryan’s phylogenetic found it to be the most basal centrosaurine known.

Ryan, M.J. (2007). A new basal centrosaurine ceratopsid from the Oldman Formation, southeastern Alberta. Journal of Paleontology 81(2):376-396.

If dinosaurs hadn't gone extinct: the evolution of dinosauroids

Horizon: My Pet Dinosaur was broadcast on BBC Two on 13 March at 21:00GMT. The idea behind the program is what would have happened if the dinosaurs hadn’t gone extinct? This sounds like a fantastic idea for a program and I am all for popularizing science, I believe public interest in scientific research is important. But some of these popularizations go to far; there are bound to be small anatomical mistakes in TV shows, even some hypotheses based on limited evidence, but what I hate is unreined wild speculation.

Several palaeontologists including Kristi Curry-Rogers and Phil Currie lent their names to this show and make reasonable statements about a world of dinosaurs today including:
“Adaptable dinosaurs had it all covered. Dinosaurs could have comfortably colonised many environments, from polar conditions to regions of rivers and forests, jungle and deserts”.
"We wouldn't have the modern animals that we're used to. Giraffes and elephants and so on; they just wouldn't have evolved because dinosaurs would still be here.”

But the show then goes on to state that dinosaurs like the bipedal Troodon with its good vision, long grasping hands and problem-solving abilities made it a candidate for a human-like evolutionary path.

Dr Simon Conway Morris says: "The human is extraordinarily well designed," he says. The whole arrangement is actually designed for a particular mode of life, which, as you can see looking around us, is incredibly successful…If it's such a good solution for us, is it so difficult to imagine it could be a good solution for a dinosaur, therefore a 'dinosauroid'?"

The show even includes full-sized, bold constructions of ‘dinosauroids’. Ok so maybe I am being to harsh and this is just a little fun, but I like my popular science to at least have some element of science.

CSI: Garfield County

I have been watching way too much CSI. For those who haven’t seen the popular American television show, it is about a team of highly skilled Crime Scene Investigators who use keen observational skills and high tech gadgetry to solve crimes each week in Las Vegas (The franchise also includes Miami and New York).

Well on the way to the coffee house yesterday my husband, Paul, spotted a trail of blood, obviously a fight at one of the local clubs the night before. I know we have been watching too much CSI because before the end of the block we had determined the trail we were examining was the result of gravitational blood splatter (GBS) from two wounds on a single victim heading up Queen’s Road. Paul wouldn’t let me keep following the trail after we got to the coffee shop so unfortunately you will have to wait to hear about my findings until I can go back to take a look.

I found myself thinking along the same lines when I read a news article this week about a spectacular Montana find: a team of fossil hunters in the badlands of western Garfield County have found a unusual pair of creatures frozen in time: a theropod and a ceratopian dinosaur. The pair died near the coast of Montana's prehistoric sea 75 million years ago and the sediment preserved remarkable detail. The theropod resembles a Gorgosaur and the unidentified ceratopian has a frill like a triceratops but no horns. Slightly bittersweet, the theropod skeleton is marred by a single flaw: one missing claw keeps it from being 100% complete.

The discovery is believed to be one of only three that have ever captured a carnivorous and herbivorous dinosaur together, and the first in North America. As the excavators cleared the sandstone, they found four carnivore teeth lodged in the vegetarian's cervical and thoracic vertebrae (Queue: Who are you….? Who? Who? Who? Who?).

At first glance it may seem that we may have solved a millions of years old cold case but palaeontologist Nate Murphy claims that the evidence against the theropod suspect is circumstantial only. Based on the placement of the skeletons he thinks it is more likely that the two were the unfortunate victims of a flood. He believes that the herbivore was attacked before it met the suspect, who at worst was guilty of stalking its prey. I however believe the real answer may lie in the missing claw…

On another note, the discovery has stirred up the controversial issue commercial fossil hunting. Especially since some of the fossil hunters believe this discovery is in the league of "Sue," the largest and most complete T. rex found. Though Sue eventually found her home in the Chicago Field Museum, she was the center of a five year long custody battle between three parties which ended in a sale of $8 million provided through corporate sponsorship.

You can read more about the spectacular Montana find on the website of the Great Falls Tribune.