Race for the Double Helix

The Watson-Crick model of DNA was a Nobel Prize winning structure. But what differed from this one to all of the other DNA structures that already existed? Well, Watson and Crick discovered the DNA was double-helical. Previously it was believed that DNA had a triple helix. Watson and Crick knew that the phosphates could not be located on the outside while the bases were on the inside.

The novel feature of their structure was that the two chains were held together by a purine and pyrimidine base. They are joined in pairs, a single base from one chain being hydrogen-bonded to a single base from the other chain, so that the two lie side by side with identical z-co-ordinates. Adenine (purine) is paired with thymine  (pyrimidine), and guanine (purine) is paired with cytosine (pyrimidine). Many times it will be written like: A-T, G-C.

As we already know, DNA consists of two strands, and each of those strands consist of a phosphate-sugar-phosphate backbone with bases (A, T, C or G) on the sugar molecules. The two strands run opposite of each other, with the bases pointing inwards and (as mentioned above) adenine is always paired with thymine, and guanine is always paired with cytosine. Therefore, if you know the sequence of one strand, then you know the sequence of the other strand. They are mirror images in reverse.

The Controversy behind the Discovery

Most of you may know that DNA, or deoxyribonucleic acid, structure was discovered by a team of scientists: James Watson, Francis Crick, and Maurice Wilkins, but there was also another key person who helped lead them to their discovery, Rosalind Franklin. So why was the Nobel Prize for the discovery of the structure of DNA awarded to only Watson, Crick and Williams and not Franklin? That is an excellent question.  I know it sounds like an awful argument to make, but it more than likely is due to the fact that she was a woman.

Franklin obviously was not credited for her help in the discovery of the DNA structure. If it weren’t for the picture she had taken, Watson and his teammates would never have made their discovery. She laid the basis for the quantitative study of the diffraction patterns, and after the formation of the Watson - Crick model she demonstrated that a double helix was consistent with the X-ray patterns of both the A and B forms of the molecule.

In 1951, Rosalind returned to England as a research associate in John Randall's laboratory at King's College, London. While working there she crossed paths with Maurice Wilkins. They both led separate research groups and had separate projects, although both were concerned with DNA. Randall gave Franklin responsibility for her DNA project, and when Wilkins returned from an absence he did not understand her role and treated her like a technical assistant. At the time, women did not receive the same rights as men. Only males were allowed in the university dining rooms, and after hours Franklin's colleagues went to men-only pubs.

The friction between Franklin and Wilkins grew, although they considered themselves friends. One day Wilkins showed James Watson a crystallographic portrait of DNA that Franklin had taken. She was very close to the discovery of the structure at this point, but close only comes in horse shoes and hand grenades. As soon as Watson saw the pictures the solution became apparent to him, and the results went into an article in Nature almost immediately. By the time Watson, Wilkins, and Crick received the Nobel Prize, Franklin had died from cancer.

In the last few years there has been a similar controversy and billion dollar law suit over a stolen idea, Facebook. Apparently Mark Zuckerberg stole the idea of this social networking site from the Winklevoss brothers while attending school at Harvard. Only in this case, the Winklevoss's received a settlement agreement onn February, 2008, for $20 million in cash and 1,253,326 Facebook shares. Not too shabby, huh?

In order to prevent another Franklin/Watson episode, I believe the scientific community should have to have strict rules on citing where and when you did your research and if you use any pictures you must get permission from the person who took the picture to conduct research on it or to use it as evidence.

GATTACA

It has been a while since the last time I have blogged about the exciting world of science! Well, I'm back! If you haven't already, I highly suggest that you either rent, buy, download or Netflix the movie, GATTACA! At first, I was nervous that the movie was going to be a very "low-budget", cheaply made science fiction movie that all biology classes watch because it's about DNA and genetic engineering. Well let me tell you: the movie was fantastic! I was on the edge of my seat, AND I also learned a thing or to about science. I suggest that before you read this blog, you visit one of my favorite websites, imdb.com, to read the synopsis of the movie, and see the actors that star in this great film.

However, if you are too lazy to click on the link, I will give you a brief story-line that I found on imdb.com, which was written by garykmcd.

"In the not-too-distant future, a less-than-perfect man wants to travel to the stars. Society has categorized Vincent Freeman as less than suitable given his genetic make-up and he has become one of the underclass of humans that are only useful for menial jobs. To move ahead, he assumes the identity of Jerome Morrow, a perfect genetic specimen who is a paraplegic as a result of a car accident. With professional advice, Vincent learns to deceive DNA and urine sample testing. Just when he is finally scheduled for a space mission, his program director is killed and the police begin an investigation, jeopardizing his secret."

Ta-DA! Now that you know what the movie is about, you will have a better understanding of my blog.

Having a society of superior genetic engineering, like that portrayed in GATTACA, comes many advantages and disadvantages. To name a few obvious advantages: you would have a longer life span, less chance of developing any disease or physical abnormality, your IQ would be unbelievable! Basically, you would be able to reach your full potential, guaranteed. Well, that is, if you were a "valid" or genetically engineered by your parents and their physician. In Vincent Freeman's case, he was a "in-valid" , a "faith baby", a "God-child" and therefore, looked down upon. He was not perfect and thus, he did not fit into his perfect society. I believe that being perfect would be boring. The perfect society in the movie would become very blasé, very quickly.

The eccentric, the different, the misfits and the weak of our society, make us what we are: human. In my opinion, there is no such thing as being perfect. Just for the sake of things though, if our society was able to be "perfect" we would still see desired traits in some people, and strive to be more like them. We would still categorize people. It is part of our human nature to categorize people...it's just what we do. But without these unique people in the world, I feel our society would be very uncreative and rather boring.

I believe limits should be placed on genetic engineering. I am not sure where you would draw the line though. That is a very ethical question that is hard to answer. If I were born with a physical abnormality or disease, I would wish that something had been done to prevent that. But I think we are trying to hard to play God, so maybe we shouldn't even use it to eliminate disease and physical imperfections. Once again, if that technology was available and I had a child that was suffering, I know I would wish I had done something to prevent it.

Genetic engineering is rapidly developing and improving. A few generations from now, I bet parents will have the opportunity to pick and choose desired traits they want their child to have. Should we let that happen? I guess that is something you must decide for yourself.

GERM-X

germ-X is an example of a disinfectant.

Eww. Bacteria.

Have you ever wondered just how well certain cleaning agents work? How much bacteria do they really kill? My biology class recently did a lab to test the efficiency of common antibacterial products.

You may know that bacteria are some of the simplest and most numerous life forms on Earth. In fact, there are approximately ten times as many bacteria cells in the human flora than there are human cells in the body. Not all bacteria is bad though. In fact, bacteria is vital to all life forms! They even help in the production of foods like cheese and yogurt. We all know that there are also harmful bacteria out there just waiting to infect our bodies!! We use antibacterial and antimicrobial soaps to kill off these pesky little single cellular organisms when we wash our hands.

Disinfectants can only be used on non-living objects. Some examples of disinfectants include bleach, rubbing alcohol, and Germ-X. If and living organism digested a disinfectant they would either have to rush to a posion control specialist, or die. Antiseptics are antimicrobial substances that can be applied to living tissue/skin. Examples of antiseptics include mouthwash and soap. Isopropyl alcohol can be used as both a disinfectant and antiseptic.

Common household cleaning agents, such as disinfectants and antiseptics, do the same---they kill bacteria. You can think of it as World War III: Humans vs. Microorganisms. Our society has become anti-bacteria CRAZED. In fact, our obsession with being super clean causes some scientists to sit on the edge of their seats. They are worried that our bacterial resistance will lead to the development of resistant strains that our disinfectants and antiseptics can no longer fight off.

During our lab, we did two trials. The first one we swabbed our skin and the second trial we got to swab any non living surface to see how much bacteria was growing there. During the skin trial we swabbed our "dirty hands" (we weren't allowed to wash our hands for several hours prior to our lab) with a sterile cotton swab that was dipped in distilled water, then a new swab dipped in isopropyl alcohol, and finally we washed our hands with antibacterial soap and swabbed our hand with a new cotton swab before we tried our hands off. After each swabbing we zig zagged the cotton swab in one of the 6 sections of our petri plate of agar that looked like this.

After our skin trial, we moved on to our surface trial. I decided to pick the knob of one of the sinks in the girls lockerroom since it probably got quite a bit of action and probably not very high on the priority level of the janitorial staff. The three treatments (cotton swabs) that we used for this trial were distilled water, alcohol, and bleach. The bleach treatment worked the best in the surface trial, for after the petri dish incubated, there was no bacterial growth in the bleach section of the agar.

LAVA

Recently my biology class did a lava lamp lab! We used a water bottle, vegetable oil, tap water, food coloring, and Alka Seltzer tablets. So, it wasn't an actual lava lamp...but it was pretty fun and easy to make! After doing our lab, we were asked to research the science behind a real lava lamp.

Interestingly enough, a real lava lamp isn't much different from the ones we made. The theory behind how a lava lamp (also known as a "liquid motion lamp") is that there are two liquids involved that are very close in density, and insoluable to one another. When you pour water and oil into a container, the water will sink below the oil due to the water having a higher density than the oil. Water and oil do not mix because an oil molecule is hydrophobic, or water fearing, so its molecules do not bond to the hydrogen molecules of the water.

When we added the food coloring, it only adhered to the water because the food coloring is hydrophilic, or water loving. The food coloring is able to bond to the water molecules, and thus the oil remains colorless. This is the same as in a real lava lamp. When you see the globs of "lava" bubbling and floating, you are really just seeing colored water ---sorry if you thought there was actual lava in lava lamps and I just spoiled your fun!

To actually make our "lava", we added Alka Seltzer tablets which chemically reacts when dropped into water because it contains citric acid and sodium bicarbonate, which produces the "fizz". This fizz was the energy source that moved our colored water to the top of the oil, and then the water sank back to the bottom of the water bottle, below the oil.  In a real lava lamp, the energy source is the heat from a light bulb. When the water becomes heated, it becomes less dense and floats to the top of the oil. As it cools down, it returns to its original location below the oil. This process continues, and gives the lava lamp it's unique characteristic.

Quorum Sensing

Many people have never heard of the term, "quorum sensing", which is most likely because it is a relatively new concept. Princeton's Bonnie Bassler and her team of scientists (which consist of her students) have developed a theory of how bacteria communicate with eachother. PBS got an excellent interview with Bassler a few years ago.

 So how exactly does quorum sensing work? Well, as the bacteria grows, it releases a small amount of chemicals called "auto-inducers". The chemical is proportional to the amount of bacteria cells. At first there is just a small amount of the chemical floating around, but after the cells replicate there is more of this chemical. The bacteria can sense with antennae-like sensors on their membrane that there is a significant amount of auto-inducers, and they begin to grab it and take hold. Because of this sensing, they now know that there is enough bacteria cells to do some damage, so to speak. It's basically like the concept that there is "strength in numbers". If just a few little bacteria cells released toxins into the body, it would be very easy for our immune system to identify that there is a toxic foreign substance in our body and fight of the bacteria, but when there is an unfathomable amount of bacteria it is harder for our immune system to fight it off. Your body is covered with bacteria! Your gut alone contains 10¹⁰ bacterial cells. Don't freak out and go stock up on antibiotics--many of the bacteria found in your body are helpful. People used to believe that bacteria cells were asocial, meaning they do not communicate between eachother, for they are unicellulor organisms. They only have one piece of DNA inside of them, making them the simplist for of organism. Bassler questioned the bacteria's actions and the body's response once being attacked: why doesn't the body fight of the bacteria as soon as it releases toxin? It would be much easier to fight off bacteria before it starts asexually reproducing and replicating. After much research, her team discovered that the bacteria chemically communicates with eachother and waits to release toxins until there are roughly 10⁸ or 10⁹ acting against you simultaneously. Smart, huh? It makes it much harder for the body's immune system to fight off such an extravagent amount of bacteria cells, compared to just a few hundred.

There is a certain type of bacteria that is responsible for bioluminescence called Vibrio harveyi.  It produces light due to quorum sensing. Bassler's team discovered that single cells of Vibrio harveyi do not illuminate by themselves. They wait until they have more cells in their colony before they illuminate.

Bassler hopes to some day be able to control quorum sensing and be able to put it into a practical application, such as making insulin from good bacteria and pro-biotics to help us from getting sick in the first place.