Monday, September 16, 2013

Of Chickens and Viruses

If you live in the US, you most likely have two egg-color options at your grocery store or farmers' market: white or brown. The color of these eggs doesn't affect flavor or nutritional content of the eggs - it just depends on the breed of chicken that layed them. However, if you have a Araucana, Dongxiang, or Lushi chicken (and if you do, you probably don't live in North America) they will probably lay blue eggs. A recent study in PLoS Genetics has shown that the reason for this is a retrovirus, EAV-HP, that has affected the chicken and turned it's eggs blue. But how can a virus affect eggs color?

The answer lies in how retroviruses work. Retroviruses use RNA as their genetic material (instead of DNA like we do). However, when the virus infects a host cell, it uses an enzyme called Reverse Transcriptase to translate it's RNA genome into DNA. This DNA is then inserted into the host cells' DNA genome, essentially tricking the host cell into using the information in the new DNA to make more retroviruses. The most famous retrovirus that affects humans is probably the Human Immunodeficiency Virus, shown in the image above (green) infecting a human lymphocyte (pink). Sometimes, when a retrovirus inserts a gene into the host DNA, it can change or affect the expression of genes around the insertion point. This is what happened with the blue egg-laying chickens.

In the case of EAV-HP, the virus inserted near a gene for a membrane transporter called SLCO1B3 and turned it on in the chicken uterus. This change allows the developing eggs to take up a bile pigment called biliverden from the chicken's body, turning the egg blue. Because this gene became part of the chicken's DNA, it is able to pass on the trait to it's offspring. Due to preferential breeding of Araucana, Dongxiang, or Lushi chickens that have this trait, most chickens of these breeds now lay blue eggs. The exact DNA sequences near theSLCO1B3 genes in these breeds is different, suggesting that the retrovirus caused the DNA changes that result in blue eggs in independent events in all three breeds. Both the blue pigment and the retrovirus involved are completely harmless to humans, so if you see a blue egg, don't hesitate to fry it up and enjoy!

(via BoingBoing)
(Image: Human Immunodeficiency Virus (HIV-I), a Creative Commons 2.0-licenses image from Microbe World's photostream)

Wednesday, August 21, 2013

Happy lobster month!

I'm not sure how this has not come to my attention sooner, but August is Maine Lobster Month! Lobsters are, by my estimation, the tastiest arthropods. Maybe some people would disagree.

When you picture a delicious lobster, ready to eat, it's bright red in color. On the other hand, if you've ever fished one out of the ocean (or seen it done) you know that live lobsters aren't that color at all - they're generally brownish. In honor of lobster month, here is an interesting video about why lobsters turn bright red when you cook them. Enjoy!

Bonus fact: Lobsters are colorful in another way - they have blue blood (like spiders and some other crustaceans), thanks to hemocyanin, a protein that transports oxygen in their blood using copper. Our blood and the blood of many other vertebrates is red because of hemoglobin, which uses iron to transport oxygen.

(Thanks to Life Lines blog for the link!)

Thursday, July 11, 2013

2013: The Year of Quinoa

Have you heard of quinoa? If you're one of the millions that shops at specialty groceries like Trader Joe's or Whole Foods, you probably have. It's an ancient grain, grown mainly in South America, which has become quite trendy in the us in recent years, and as a result has gotten more expensive. Can we expect the price to go down as the quinoa supply increases to meet rising demand? Maybe, and maybe not.

An interesting post at the Washington Post Wonkblog (with graphs!) gets into the economic reasons why quinoa farmers are not cropping up all over the world. Mostly, there is an enormous startup cost to growing a new species of plant on a large scale, or in a new environment. Producing more quinoa in the US, for example, would require both. Getting more quinoa from the farmers in Bolivia and Peru that have been growing the grain for centuries isn't such an easy proposition, either, as these traditional farmers use older techniques and equipment that are not so easily scaled up as are industrial agricultural methods. A number of solutions are being studied, including new varieties of quinoa that can grow in different climates. These topics will be discussed at an upcoming quinoa symposium.

Why are we eating so much quinoa? Well, aside from the facts that we love novelty the latest health food fad, quinoa is tasty and actually healthy. It's about 14% protein, which is a lot for something we consider a grain (although not as high as beans), and it is a vegetarian source of "complete protein," meaning that it contains all the amino acids that our body cannot synthesize on its own and needs to get from our diet. It's also high in fiber and a number of other nutrients like B vitamins and iron. So, eat your quinoa, if you can afford it, and hope that in the future, there will be enough to go around.

Also, here is a fun quinoa bonus fact from Wikipedia: While quinoa is not a true grass like the cereal crops we think of as grains (wheat, rice, etc.), it is closely related to tumbleweeds.

A tip of the hat to Ragan for the article!
(Image: Quinoa, a Creative Commons 2.0 licensed image from Renee S. Suen's Photostream)

Saturday, February 23, 2013

Science of Addiction: Junk Food Edition

Everybody knows that we shouldn't eat so much processed junk food, and everybody also knows that's it's sometimes difficult to control your intake of these foods. However, I don't think that many people have thought about what goes on in your brain when you eat many more potato chips than you had planned to eat. In the NYT this week there  is a very interesting piece addressing just these issues and the research that has contributed to our current understanding of why humans love junk food.

For the past 50 years or so, a great deal of research has gone into what it is that humans like to eat and how to market it to them, beginning with military research into which MREs soldiers prefer and continuing to the modern day with research into how many pounds per square inch of pressure it takes to break the ideal potato chip and how to successfully market baby carrots as snack food. Most of this research has been done by large processed food companies with an eye to idealizing the taste of their snack foods so that people will eat more of them. By most accounts, they have been wildly successful - so successful that in the U.S. today one in three adults is obese and the rate of type II diabetes climbs  every year.

One interesting tidbit from the article is that research shows that, although we like strong or unique tasting foods for a short time, we quickly tire of them if we eat the same one over and over again. Over the long term, we will eat more of relatively bland but tasty foods (like white bread and potato chips). This is great news for the makers of salty, fatty, but unremarkable snack foods (I'm looking at you, Cheetos!) that we know so well.

There is a growing awareness that the types of foods, especially processed foods, that people eat contributes to (or detracts from) their health as much, if not more, than the quantity of that food. As I learned from this article, even people involved with marketing processed foods to the public are acknowledging that what we eat is part of the growing health crisis in our country.

Hopefully in the future we can put all of the research behind marketing and idealizing unhealthy food to work helping people to make better choices about what they eat. The more we understand about why people like certain foods, the more we can make healthy foods that people like to eat, or at least stop making and eating addictive foods that ultimately make us sick. The solution to the problem will have to be a combination of information that consumers can use to make better food choices and more responsible food manufacturing and marketing by the handful of companies that control the majority of processed food in America. Understanding what is going wrong now is the first step in the right direction.

(Image: Junk food, grocery store, Houston, TX, USA, a Creative Commons 2.0 licensed image from Cory Doctorow's Photostream via BoingBoing)