"What is a weed? A weed is a plant whose virtues have not yet been discovered." – Ralph Waldo Emerson

Almost every winter my family gets poinsettias, not Christmas trees, to deck the house. These plants are the ideal Christmas décor with their green and red leaves. Yes, red leaves. From afar, many people think the red parts are the petals, but actually they are bracts, modified leaves located below the flowering region. The real flowers (aka cyathia) are yellow and found in the center of each leaf bunch.

A poinsettia proudly shows off its bright red and green leaves.

Although we associate poinsettias with winter, they are typically found in deciduous tropical forests in Mexico and Central America. The Aztecs had cultivated them to make dyes and treat fevers. The plant’s association with Christmas originates in 16th century Mexico. According to legend, there was a girl who was too poor to bring a gift for baby Jesus on his birthday. An angel inspired her to gather weeds and place them at the church altar. Soon after, the weeds sprouted bright red leaves and became poinsettias. In reality, wild poinsettias are considered weeds.

The name poinsettia comes from Dr. Joel Poinsett, the first US ambassador to Mexico (he co-founded the National Institute for the Promotion of Science and the Useful Arts, the predecessor of the Smithsonian Institution!). He introduced them to the US in the 1820s, but we can thank Paul Ecke, Jr., for making poinsettias holiday plants. He suggested growing poinsettia cuttings in greenhouses, allowing for the development of colorful varieties of these plants. He also advertised them on TV and in newspapers, even going as far as putting them on Bob Hope’s Christmas specials.

Despite its Christmas connotation, poinsettias should still be grown at normal room temperature, receive about 6 hours of indirect sunlight each, day, and never experience temperatures below 50 degrees. Also, be sure to hide them from your pets! Although the idea that poinsettia leaves are toxic is a myth, the milky latex can cause an allergic reaction, so try to keep your dog from feeling miserable during the holiday festivities!

Ok, so the crimson red is a pretty sight to see on these plants, but wouldn’t it be super cool if these plants glowed in the dark?! Scientists have already started doing this with the tobacco plant! . These plants are genetically modified so that they can glow as a natural part of their life cycle and not depend on any chemicals or external black light sources (like fireflies!). Scientists inserted genes that make special marine bacteria glow into these plants. I actually saw these bacteria in the waters of Woods Hole, MA, and Fajardo, Puerto Rico. When they sense agitation in the waters, they release light! Since these genes make bacteria glow, the scientists thought it'd be cool to make other stuff glow. So they put the genes (for you science-savvy people, the genes encode for luciferase, an enzyme that makes the light-emitting reaction) into the DNA of plant plastids. Plastids are the structures that contain the color-producing molecules. Although the light that the plants emit is rather dim, the researchers are trying to make it brighter!

Location of the glowing bacteria (Woods Hole, MA)

The scientists are associated with BioGlow Tech (http://bioglowtech.com/), a company that wishes to create glowing plants for ornamental plant growers. So don’t be surprised to see a glowing poinsettia replace your artificially lit Christmas tree in the near future!

     Ok, not a glowing poinsettia tree but still a pretty one! Photo credit: Hema Sundaresan

Happy holidays!

(By the way, December 12 is Poinsettia Day!)

“Rocks are records of events that took place at the time they formed. They are books. They have a different vocabulary, a different alphabet, but you learn how to read them.” -John McPhee

Every day, I see East Rock from my lab’s 6^th floor lounge. This place (East Rock, not my lab) is one of the few interesting places to go to in New Haven. There are nice trails, great picnic spots (my PhD class had a year-end barbecue there; holla Megatrackers!), and a lovely view of all of New Haven and the Long Island Sound. And, of course, the ominous Kline Biology Tower (home to the Molecular, Cellular, and Developmental Biology Department) sticks out like sore thumb. Fortunately, the lab building I'm in is much prettier :) Anyway, enchanted by this geologic feature, I decided to Wiki “East Rock” and was intrigued to learn that it is actually a trap rock ridge. I had never heard such a term before, so I decided to do some more research on it.

View of New Haven from the top of East Rock. Photo credit: Nikhil Bumb

Trap rock ridges, which are known for their rust colored cliffs, are quite common in Connecticut and Massachusetts. Their name comes from the dense, dark, fine grained igneous rock of which they are made. However, “trap rock” is a mining, not geologic, term to describe dark igneous rocks used for road construction. When dark magma originating from the Earth’s mantle extrudes into the crust, it cools slowly and becomes the coarse-grained gabbro rock. However, when the magma gets to the surface, it cools faster, becoming the fine-grained basalt rock that makes up East Rock. Fresh basalt is grey, but after centuries of weathering, the iron in the rock begins to rust, giving the distinctive red color. The weathering also fractures the basalt into the distinctive octagonal and pentagonal columns.

The rust-colored columns that define East Rock.

As hinted before, volcanic activity (from 200 million years ago during the Triassic and Jurassic periods!) and erosion are the two big events that form these ridges. Three major lava flows from unexplosive volcanoes spilled onto the Connecticut Valley floor, which then cooled and hardened into trap rock, and over time, got covered with sediment and stuck into brownstone. After thousands of years of erosion, the weaker brownstone and sedimentary layers were swept away into the Long Island Sound, leaving the more resistant basalt sheets exposed and abruptly tilted. The result is the cliff-faced East Rock we see and enjoy today!

Sources: http://www.wesleyan.edu/ctgeology/Traprock.PDF 

              http://www.mii.org/Minerals/phototraprock.html

"DNA neither cares nor knows. DNA just is. And we dance to its music." - Richard Dawkins

Deoxyribonucleic acid.  My first memory of that phrase was from watching Bill Nye the Science Guy in elementary school (Hey, I’m pretty sure you all watched that show, so don’t call me a nerd!).  I could barely pronounce the whole thing.  I remember my friends and I would have contests to see who could say it the most number of times in a minute without faltering.  Little did I appreciate this building block of life until I attended a summer science camp before my senior year of high school (OK, I’m a nerd). 

The 3-week intensive program consisted of classes in various areas of math and science as well as lab sessions. In our biology lab session, we extracted DNA from vegetables (you can do it yourself!).  It was pretty cool to have the genetic material of an onion right at my fingertips (well, pipette tip).  It doesn’t look anything special, though.  It’s white and stringy, and no, you can’t see the actual double helix! We also performed PCR (polymerase chain reaction), a process that amplifies DNA in order to create a sufficient amount of it to properly analyze the product. 

 

I soon found out later in my research career that PCR pretty much defines the life of a scientist.  We use it so much that songs have been made about PCR and its reagents.  The PCR products are eventually run on a gel.  If this sounds foreign to you, think CSI.  This is how they figure out who the murder is (and even who the daddy is! Refer to the first PCR song).  Basically, DNA is injected into an agar block with wells indented into it.  I was initially terrified of injecting the DNA because if you pushed the tip too far into the gel, the DNA would leak out of its designated well, all hell would break loose, toilets would start flushing in the opposite direction, and your dreams of becoming a scientist were shattered (or so I thought).  Believe me, one needs steady arms and hands for loading the DNA, but now I can practically do it in my sleep!  The tray containing the gel with the DNA loaded on it is put in a box hooked up to a voltage source.  When the current is turned on, the DNA migrates down the gel, moving from the negative to positive electrode. Why? DNA is a negative molecule, so naturally, it is attracted to the positive charge! After running the gel for about 30 minutes, it is viewed under UV light.  The gel is previously stained with ethidium bromide, which physically interacts with the DNA, allowing the DNA to fluoresce under UV light.  A ladder with known DNA sizes is also run along the DNA.  Thus, one can estimate the size of the DNA based on the ladder size.  And voila!  Now you know “who dunnit” based on whether the sizes of the victim's and suspect's DNA match up.  Of course, this technology is not only used to solve crimes, but also to help make many scientific discoveries!

 

This lab experience made me realize not only how important DNA is to life but even to applications in life.  Now I am passing on this skill to middle school students!  Through a science outreach program, I helped some grad student TAs with a lab in which the kids themselves extracted DNA from their cheeks and practiced loading gels (they were much better than I was on my first try!).

 

I came to appreciate the history of DNA when I studied abroad in King’s College London during the fall semester of my Junior year.  It was here that Rosalind Franklin and Maurice Wilkins used X-ray diffraction to understand the physical structure of the DNA molecule, during the fall semester of my Junior year.  I saw the semi-original model made famous by James Watson and Francis Crick, displayed in the Science Museum in London.

Semi-original DNA model. London Science Museum.

Seeing the model made me realize how the simple beauty of the nucleotide base pairing that occurs to create this double helix. Why did nature decide to just stick to two strands?  Linus Pauling, who won the Nobel Prize in Chemistry in 1954 for his work on chemical bonds and crystal structures, published a paper in 1953 where he proposed that DNA existed as a triple helix.  Watson and Crick also incorrectly calculated the DNA to be a triple helix in 1951 based on Watson incorrectly remembering the facts and figures from a talk by Rosalind Franklin, who was working on the DNA X-ray crystallography data at King’s College. It was actually Franklin's "photograph 51", a picture of crystallized DNA that showed an “X” in the middle of the molecule, thus revealing the helical structure.

A few weeks later I visited Cambridge. I saw the outside of the Cavendish lab where Watson and Crick worked out the structure of DNA, and had lunch at the Eagle, the pub where Watson and Crick frequently discussed their ideas. Most of what I knew about Watson was of his early years at this lab.  I had not kept up with his recent musings until I had planned to attend a lecture by Watson at the museum. Unfortunately, a week before the lecture, he made his infamous remark questioning the intelligence capacity of people of African descent. 

 

Yeah, DNA is pretty awesome (all you protein lovers ain’t got nothin’ on us!).  As a grad student I am studying DNA modifications in immune cells. My work in undergrad focused mainly on nucleic acid research, but specifically on RNA, DNA’s alter ego. This post is dedicated solely to DNA, but to find out more about the RNA world hypothesis, which states that RNA was existed way before DNA and proteins, check out this page from the Nobel prize site: http://nobelprize.org/nobel_prizes/chemistry/articles/altman/, or check out the book The RNA World, 3^rd Ed.