Friday Roundup: Arsenic in juice, self-medicating chimps, science tattoos, Guinness Record-setting science cheerleaders, and more!



Are you getting regular mammograms on the recommended schedule?
Please be sure to monitor your breast health.
Health
  • Writing for Forbes, Susannah Breslin tells the story of “The business about my breasts,” chronicling her journey from mammogram to a diagnosis of breast cancer. You can follow her on Twitter here and read her blog here. Just another reason for you to ask not what science can do for you but what you can do for science
  • A UK study finds that homebirth in specifically low-risk women carries no increased risk for women who have had children previously. They assessed data for 64,538 women and found, after a whole lot of statistical adjustment, that there were no increased odds of negative outcomes for women having birth at home or midwife-attended births in facilities. They did find an increased risk for women who were trying to have planned home births who were giving birth for the first time.
  • Can eating baked or grilled fish three times a week be protective against Alzheimer’s in the elderly? These researchers think so
  • The FDA is thinking about lowering the standard it’s set for how much arsenic exposure is OK in apple and other juices. Cutoffs are usually set in what are known as “parts per billion” (ppb). That means what you think: if the cutoff is 3 ppb, that means, for example, three drops in a billion drops. Right now, the cutoff for arsenic in drinking water is 10 ppb, and consumer groups are asking the EPA to drop that to 3 ppb. Deborah Blum has addressed the fact that arsenic is present in food, water, and soil and that different forms of it have different effects. As always, it’s not as simple as hollering “toxic metal!” and calling for its removal. 
  • Can heading the ball in soccer/football cause brain damage?
  • Is a “Mediterranean-ish” diet good for your heart? Researchers draw that conclusion from this study of 2500 Manhattanites. 
  • Can dreams predict the future? No.
  • Would you want to see yourself old?


      Our Living World
      • Chimps self medicate with food. They really are our closest living relatives.
      • Speaking of being like us, some dinosaurs cared for their young, as this fossilized nest of 15 baby dinosaurs seems to suggest.
      • Looking for the animal with the most amazing, the strangest, the most remarkable nose around? Look no more. It’s the star-nosed mole:

      • Need a break from the workaday world? Listen to some whale songs and help scientists translate the language of whales.
      • Speaking of whales, scientists have sunk a 67-foot fin whale carcass off of the San Diego coast. Why go to the trouble? Whale fall is an important contribution to ocean ecosystems, and the researchers plan to study how an entire ecosystem builds up around the sunken cetacean. Here’s a video of the community that forms around a whale fall:

      Women and women in science
      • Nicole Ostrowsky shares her love of science in her book, An Agenda of an Apprentice Scientist. She also shares her love of science–and inspires it in others–as a teacher. As she notes, to teach science well to non-scientists, “You have to master subject to explain it simply.” 
      • Do you think you apologize too much
      • From the Science Cheerleader, a Guinness World Record Cheer for Science:

      • What do Marie Curie, theater, and Alan Alda have in common? Find out here as Alan Alda chats with Scientific American’s Jason Goldman. 
      • Do women lack ambition compared to men? No
      • Do science kits for girls really have to look like this? No, they do not, and one company has responded to complaints in the women-in-science blogosphere. 
      • Women are mean! Science says so! Some of us disagree.
      • Speaking of stereotypes about women and women in science, Wendy Lawrence writes about attracting girls to math and science and struggling against those stereotypes.
      • Here Come the Math Girls! In a day and age when girls are discouraged from being good at math by either being told they aren’t good or should not be, here is a refreshing book out of Japan.
      • And by way of Improbable Research: Moms on the Net: Intro to Computer Science 
      Sex


        Art and Science

        Biology Explainer: The big 4 building blocks of life–carbohydrates, fats, proteins, and nucleic acids

        The short version
        • The four basic categories of molecules for building life are carbohydrates, lipids, proteins, and nucleic acids.
        • Carbohydrates serve many purposes, from energy to structure to chemical communication, as monomers or polymers.
        • Lipids, which are hydrophobic, also have different purposes, including energy storage, structure, and signaling.
        • Proteins, made of amino acids in up to four structural levels, are involved in just about every process of life.                                                                                                      
        • The nucleic acids DNA and RNA consist of four nucleotide building blocks, and each has different purposes.
        The longer version
        Life is so diverse and unwieldy, it may surprise you to learn that we can break it down into four basic categories of molecules. Possibly even more implausible is the fact that two of these categories of large molecules themselves break down into a surprisingly small number of building blocks. The proteins that make up all of the living things on this planet and ensure their appropriate structure and smooth function consist of only 20 different kinds of building blocks. Nucleic acids, specifically DNA, are even more basic: only four different kinds of molecules provide the materials to build the countless different genetic codes that translate into all the different walking, swimming, crawling, oozing, and/or photosynthesizing organisms that populate the third rock from the Sun.

                                                          

        Big Molecules with Small Building Blocks

        The functional groups, assembled into building blocks on backbones of carbon atoms, can be bonded together to yield large molecules that we classify into four basic categories. These molecules, in many different permutations, are the basis for the diversity that we see among living things. They can consist of thousands of atoms, but only a handful of different kinds of atoms form them. It’s like building apartment buildings using a small selection of different materials: bricks, mortar, iron, glass, and wood. Arranged in different ways, these few materials can yield a huge variety of structures.

        We encountered functional groups and the SPHONC in Chapter 3. These components form the four categories of molecules of life. These Big Four biological molecules are carbohydrates, lipids, proteins, and nucleic acids. They can have many roles, from giving an organism structure to being involved in one of the millions of processes of living. Let’s meet each category individually and discover the basic roles of each in the structure and function of life.
        Carbohydrates

        You have met carbohydrates before, whether you know it or not. We refer to them casually as “sugars,” molecules made of carbon, hydrogen, and oxygen. A sugar molecule has a carbon backbone, usually five or six carbons in the ones we’ll discuss here, but it can be as few as three. Sugar molecules can link together in pairs or in chains or branching “trees,” either for structure or energy storage.

        When you look on a nutrition label, you’ll see reference to “sugars.” That term includes carbohydrates that provide energy, which we get from breaking the chemical bonds in a sugar called glucose. The “sugars” on a nutrition label also include those that give structure to a plant, which we call fiber. Both are important nutrients for people.

        Sugars serve many purposes. They give crunch to the cell walls of a plant or the exoskeleton of a beetle and chemical energy to the marathon runner. When attached to other molecules, like proteins or fats, they aid in communication between cells. But before we get any further into their uses, let’s talk structure.

        The sugars we encounter most in basic biology have their five or six carbons linked together in a ring. There’s no need to dive deep into organic chemistry, but there are a couple of essential things to know to interpret the standard representations of these molecules.

        Check out the sugars depicted in the figure. The top-left molecule, glucose, has six carbons, which have been numbered. The sugar to its right is the same glucose, with all but one “C” removed. The other five carbons are still there but are inferred using the conventions of organic chemistry: Anywhere there is a corner, there’s a carbon unless otherwise indicated. It might be a good exercise for you to add in a “C” over each corner so that you gain a good understanding of this convention. You should end up adding in five carbon symbols; the sixth is already given because that is conventionally included when it occurs outside of the ring.

        On the left is a glucose with all of its carbons indicated. They’re also numbered, which is important to understand now for information that comes later. On the right is the same molecule, glucose, without the carbons indicated (except for the sixth one). Wherever there is a corner, there is a carbon, unless otherwise indicated (as with the oxygen). On the bottom left is ribose, the sugar found in RNA. The sugar on the bottom right is deoxyribose. Note that at carbon 2 (*), the ribose and deoxyribose differ by a single oxygen.

        The lower left sugar in the figure is a ribose. In this depiction, the carbons, except the one outside of the ring, have not been drawn in, and they are not numbered. This is the standard way sugars are presented in texts. Can you tell how many carbons there are in this sugar? Count the corners and don’t forget the one that’s already indicated!

        If you said “five,” you are right. Ribose is a pentose (pent = five) and happens to be the sugar present in ribonucleic acid, or RNA. Think to yourself what the sugar might be in deoxyribonucleic acid, or DNA. If you thought, deoxyribose, you’d be right.

        The fourth sugar given in the figure is a deoxyribose. In organic chemistry, it’s not enough to know that corners indicate carbons. Each carbon also has a specific number, which becomes important in discussions of nucleic acids. Luckily, we get to keep our carbon counting pretty simple in basic biology. To count carbons, you start with the carbon to the right of the non-carbon corner of the molecule. The deoxyribose or ribose always looks to me like a little cupcake with a cherry on top. The “cherry” is an oxygen. To the right of that oxygen, we start counting carbons, so that corner to the right of the “cherry” is the first carbon. Now, keep counting. Here’s a little test: What is hanging down from carbon 2 of the deoxyribose?

        If you said a hydrogen (H), you are right! Now, compare the deoxyribose to the ribose. Do you see the difference in what hangs off of the carbon 2 of each sugar? You’ll see that the carbon 2 of ribose has an –OH, rather than an H. The reason the deoxyribose is called that is because the O on the second carbon of the ribose has been removed, leaving a “deoxyed” ribose. This tiny distinction between the sugars used in DNA and RNA is significant enough in biology that we use it to distinguish the two nucleic acids.

        In fact, these subtle differences in sugars mean big differences for many biological molecules. Below, you’ll find a couple of ways that apparently small changes in a sugar molecule can mean big changes in what it does. These little changes make the difference between a delicious sugar cookie and the crunchy exoskeleton of a dung beetle.

        Sugar and Fuel

        A marathon runner keeps fuel on hand in the form of “carbs,” or sugars. These fuels provide the marathoner’s straining body with the energy it needs to keep the muscles pumping. When we take in sugar like this, it often comes in the form of glucose molecules attached together in a polymer called starch. We are especially equipped to start breaking off individual glucose molecules the minute we start chewing on a starch.

        Double X Extra: A monomer is a building block (mono = one) and a polymer is a chain of monomers. With a few dozen monomers or building blocks, we get millions of different polymers. That may sound nutty until you think of the infinity of values that can be built using only the numbers 0 through 9 as building blocks or the intricate programming that is done using only a binary code of zeros and ones in different combinations.

        Our bodies then can rapidly take the single molecules, or monomers, into cells and crack open the chemical bonds to transform the energy for use. The bonds of a sugar are packed with chemical energy that we capture to build a different kind of energy-containing molecule that our muscles access easily. Most species rely on this process of capturing energy from sugars and transforming it for specific purposes.

        Polysaccharides: Fuel and Form

        Plants use the Sun’s energy to make their own glucose, and starch is actually a plant’s way of storing up that sugar. Potatoes, for example, are quite good at packing away tons of glucose molecules and are known to dieticians as a “starchy” vegetable. The glucose molecules in starch are packed fairly closely together. A string of sugar molecules bonded together through dehydration synthesis, as they are in starch, is a polymer called a polysaccharide (poly = many; saccharide = sugar). When the monomers of the polysaccharide are released, as when our bodies break them up, the reaction that releases them is called hydrolysis.

        Double X Extra: The specific reaction that hooks one monomer to another in a covalent bond is called dehydration synthesis because in making the bond–synthesizing the larger molecule–a molecule of water is removed (dehydration). The reverse is hydrolysis (hydro = water; lysis = breaking), which breaks the covalent bond by the addition of a molecule of water.

        Although plants make their own glucose and animals acquire it by eating the plants, animals can also package away the glucose they eat for later use. Animals, including humans, store glucose in a polysaccharide called glycogen, which is more branched than starch. In us, we build this energy reserve primarily in the liver and access it when our glucose levels drop.

        Whether starch or glycogen, the glucose molecules that are stored are bonded together so that all of the molecules are oriented the same way. If you view the sixth carbon of the glucose to be a “carbon flag,” you’ll see in the figure that all of the glucose molecules in starch are oriented with their carbon flags on the upper left.

        The orientation of monomers of glucose in polysaccharides can make a big difference in the use of the polymer. The glucoses in the molecule on the top are all oriented “up” and form starch. The glucoses in the molecule on the bottom alternate orientation to form cellulose, which is quite different in its function from starch.

        Storing up sugars for fuel and using them as fuel isn’t the end of the uses of sugar. In fact, sugars serve as structural molecules in a huge variety of organisms, including fungi, bacteria, plants, and insects.

        The primary structural role of a sugar is as a component of the cell wall, giving the organism support against gravity. In plants, the familiar old glucose molecule serves as one building block of the plant cell wall, but with a catch: The molecules are oriented in an alternating up-down fashion. The resulting structural sugar is called cellulose.

        That simple difference in orientation means the difference between a polysaccharide as fuel for us and a polysaccharide as structure. Insects take it step further with the polysaccharide that makes up their exoskeleton, or outer shell. Once again, the building block is glucose, arranged as it is in cellulose, in an alternating conformation. But in insects, each glucose has a little extra added on, a chemical group called an N-acetyl group. This addition of a single functional group alters the use of cellulose and turns it into a structural molecule that gives bugs that special crunchy sound when you accidentally…ahem…step on them.

        These variations on the simple theme of a basic carbon-ring-as-building-block occur again and again in biological systems. In addition to serving roles in structure and as fuel, sugars also play a role in function. The attachment of subtly different sugar molecules to a protein or a lipid is one way cells communicate chemically with one another in refined, regulated interactions. It’s as though the cells talk with each other using a specialized, sugar-based vocabulary. Typically, cells display these sugary messages to the outside world, making them available to other cells that can recognize the molecular language.

        Lipids: The Fatty Trifecta

        Starch makes for good, accessible fuel, something that we immediately attack chemically and break up for quick energy. But fats are energy that we are supposed to bank away for a good long time and break out in times of deprivation. Like sugars, fats serve several purposes, including as a dense source of energy and as a universal structural component of cell membranes everywhere.

        Fats: the Good, the Bad, the Neutral

        Turn again to a nutrition label, and you’ll see a few references to fats, also known as lipids. (Fats are slightly less confusing that sugars in that they have only two names.) The label may break down fats into categories, including trans fats, saturated fats, unsaturated fats, and cholesterol. You may have learned that trans fats are “bad” and that there is good cholesterol and bad cholesterol, but what does it all mean?

        Let’s start with what we mean when we say saturated fat. The question is, saturated with what? There is a specific kind of dietary fat call the triglyceride. As its name implies, it has a structural motif in which something is repeated three times. That something is a chain of carbons and hydrogens, hanging off in triplicate from a head made of glycerol, as the figure shows.  Those three carbon-hydrogen chains, or fatty acids, are the “tri” in a triglyceride. Chains like this can be many carbons long.

        Double X Extra: We call a fatty acid a fatty acid because it’s got a carboxylic acid attached to a fatty tail. A triglyceride consists of three of these fatty acids attached to a molecule called glycerol. Our dietary fat primarily consists of these triglycerides.

        Triglycerides come in several forms. You may recall that carbon can form several different kinds of bonds, including single bonds, as with hydrogen, and double bonds, as with itself. A chain of carbon and hydrogens can have every single available carbon bond taken by a hydrogen in single covalent bond. This scenario of hydrogen saturation yields a saturated fat. The fat is saturated to its fullest with every covalent bond taken by hydrogens single bonded to the carbons.

        Saturated fats have predictable characteristics. They lie flat easily and stick to each other, meaning that at room temperature, they form a dense solid. You will realize this if you find a little bit of fat on you to pinch. Does it feel pretty solid? That’s because animal fat is saturated fat. The fat on a steak is also solid at room temperature, and in fact, it takes a pretty high heat to loosen it up enough to become liquid. Animals are not the only organisms that produce saturated fat–avocados and coconuts also are known for their saturated fat content.

        The top graphic above depicts a triglyceride with the glycerol, acid, and three hydrocarbon tails. The tails of this saturated fat, with every possible hydrogen space occupied, lie comparatively flat on one another, and this kind of fat is solid at room temperature. The fat on the bottom, however, is unsaturated, with bends or kinks wherever two carbons have double bonded, booting a couple of hydrogens and making this fat unsaturated, or lacking some hydrogens. Because of the space between the bumps, this fat is probably not solid at room temperature, but liquid.

        You can probably now guess what an unsaturated fat is–one that has one or more hydrogens missing. Instead of single bonding with hydrogens at every available space, two or more carbons in an unsaturated fat chain will form a double bond with carbon, leaving no space for a hydrogen. Because some carbons in the chain share two pairs of electrons, they physically draw closer to one another than they do in a single bond. This tighter bonding result in a “kink” in the fatty acid chain.

        In a fat with these kinks, the three fatty acids don’t lie as densely packed with each other as they do in a saturated fat. The kinks leave spaces between them. Thus, unsaturated fats are less dense than saturated fats and often will be liquid at room temperature. A good example of a liquid unsaturated fat at room temperature is canola oil.

        A few decades ago, food scientists discovered that unsaturated fats could be resaturated or hydrogenated to behave more like saturated fats and have a longer shelf life. The process of hydrogenation–adding in hydrogens–yields trans fat. This kind of processed fat is now frowned upon and is being removed from many foods because of its associations with adverse health effects. If you check a food label and it lists among the ingredients “partially hydrogenated” oils, that can mean that the food contains trans fat.

        Double X Extra: A triglyceride can have up to three different fatty acids attached to it. Canola oil, for example, consists primarily of oleic acid, linoleic acid, and linolenic acid, all of which are unsaturated fatty acids with 18 carbons in their chains.

        Why do we take in fat anyway? Fat is a necessary nutrient for everything from our nervous systems to our circulatory health. It also, under appropriate conditions, is an excellent way to store up densely packaged energy for the times when stores are running low. We really can’t live very well without it.

        Phospholipids: An Abundant Fat

        You may have heard that oil and water don’t mix, and indeed, it is something you can observe for yourself. Drop a pat of butter–pure saturated fat–into a bowl of water and watch it just sit there. Even if you try mixing it with a spoon, it will just sit there. Now, drop a spoon of salt into the water and stir it a bit. The salt seems to vanish. You’ve just illustrated the difference between a water-fearing (hydrophobic) and a water-loving (hydrophilic) substance.

        Generally speaking, compounds that have an unequal sharing of electrons (like ions or anything with a covalent bond between oxygen and hydrogen or nitrogen and hydrogen) will be hydrophilic. The reason is that a charge or an unequal electron sharing gives the molecule polarity that allows it to interact with water through hydrogen bonds. A fat, however, consists largely of hydrogen and carbon in those long chains. Carbon and hydrogen have roughly equivalent electronegativities, and their electron-sharing relationship is relatively nonpolar. Fat, lacking in polarity, doesn’t interact with water. As the butter demonstrated, it just sits there.

        There is one exception to that little maxim about fat and water, and that exception is the phospholipid. This lipid has a special structure that makes it just right for the job it does: forming the membranes of cells. A phospholipid consists of a polar phosphate head–P and O don’t share equally–and a couple of nonpolar hydrocarbon tails, as the figure shows. If you look at the figure, you’ll see that one of the two tails has a little kick in it, thanks to a double bond between the two carbons there.

        Phospholipids form a double layer and are the major structural components of cell membranes. Their bend, or kick, in one of the hydrocarbon tails helps ensure fluidity of the cell membrane. The molecules are bipolar, with hydrophilic heads for interacting with the internal and external watery environments of the cell and hydrophobic tails that help cell membranes behave as general security guards.

        The kick and the bipolar (hydrophobic and hydrophilic) nature of the phospholipid make it the perfect molecule for building a cell membrane. A cell needs a watery outside to survive. It also needs a watery inside to survive. Thus, it must face the inside and outside worlds with something that interacts well with water. But it also must protect itself against unwanted intruders, providing a barrier that keeps unwanted things out and keeps necessary molecules in.

        Phospholipids achieve it all. They assemble into a double layer around a cell but orient to allow interaction with the watery external and internal environments. On the layer facing the inside of the cell, the phospholipids orient their polar, hydrophilic heads to the watery inner environment and their tails away from it. On the layer to the outside of the cell, they do the same.
        As the figure shows, the result is a double layer of phospholipids with each layer facing a polar, hydrophilic head to the watery environments. The tails of each layer face one another. They form a hydrophobic, fatty moat around a cell that serves as a general gatekeeper, much in the way that your skin does for you. Charged particles cannot simply slip across this fatty moat because they can’t interact with it. And to keep the fat fluid, one tail of each phospholipid has that little kick, giving the cell membrane a fluid, liquidy flow and keeping it from being solid and unforgiving at temperatures in which cells thrive.

        Steroids: Here to Pump You Up?

        Our final molecule in the lipid fatty trifecta is cholesterol. As you may have heard, there are a few different kinds of cholesterol, some of which we consider to be “good” and some of which is “bad.” The good cholesterol, high-density lipoprotein, or HDL, in part helps us out because it removes the bad cholesterol, low-density lipoprotein or LDL, from our blood. The presence of LDL is associated with inflammation of the lining of the blood vessels, which can lead to a variety of health problems.

        But cholesterol has some other reasons for existing. One of its roles is in the maintenance of cell membrane fluidity. Cholesterol is inserted throughout the lipid bilayer and serves as a block to the fatty tails that might otherwise stick together and become a bit too solid.

        Cholesterol’s other starring role as a lipid is as the starting molecule for a class of hormones we called steroids or steroid hormones. With a few snips here and additions there, cholesterol can be changed into the steroid hormones progesterone, testosterone, or estrogen. These molecules look quite similar, but they play very different roles in organisms. Testosterone, for example, generally masculinizes vertebrates (animals with backbones), while progesterone and estrogen play a role in regulating the ovulatory cycle.

        Double X Extra: A hormone is a blood-borne signaling molecule. It can be lipid based, like testosterone, or short protein, like insulin.

        Proteins

        As you progress through learning biology, one thing will become more and more clear: Most cells function primarily as protein factories. It may surprise you to learn that proteins, which we often talk about in terms of food intake, are the fundamental molecule of many of life’s processes. Enzymes, for example, form a single broad category of proteins, but there are millions of them, each one governing a small step in the molecular pathways that are required for living.

        Levels of Structure

        Amino acids are the building blocks of proteins. A few amino acids strung together is called a peptide, while many many peptides linked together form a polypeptide. When many amino acids strung together interact with each other to form a properly folded molecule, we call that molecule a protein.

        For a string of amino acids to ultimately fold up into an active protein, they must first be assembled in the correct order. The code for their assembly lies in the DNA, but once that code has been read and the amino acid chain built, we call that simple, unfolded chain the primary structure of the protein.

        This chain can consist of hundreds of amino acids that interact all along the sequence. Some amino acids are hydrophobic and some are hydrophilic. In this context, like interacts best with like, so the hydrophobic amino acids will interact with one another, and the hydrophilic amino acids will interact together. As these contacts occur along the string of molecules, different conformations will arise in different parts of the chain. We call these different conformations along the amino acid chain the protein’s secondary structure.

        Once those interactions have occurred, the protein can fold into its final, or tertiary structure and be ready to serve as an active participant in cellular processes. To achieve the tertiary structure, the amino acid chain’s secondary interactions must usually be ongoing, and the pH, temperature, and salt balance must be just right to facilitate the folding. This tertiary folding takes place through interactions of the secondary structures along the different parts of the amino acid chain.

        The final product is a properly folded protein. If we could see it with the naked eye, it might look a lot like a wadded up string of pearls, but that “wadded up” look is misleading. Protein folding is a carefully regulated process that is determined at its core by the amino acids in the chain: their hydrophobicity and hydrophilicity and how they interact together.

        In many instances, however, a complete protein consists of more than one amino acid chain, and the complete protein has two or more interacting strings of amino acids. A good example is hemoglobin in red blood cells. Its job is to grab oxygen and deliver it to the body’s tissues. A complete hemoglobin protein consists of four separate amino acid chains all properly folded into their tertiary structures and interacting as a single unit. In cases like this involving two or more interacting amino acid chains, we say that the final protein has a quaternary structure. Some proteins can consist of as many as a dozen interacting chains, behaving as a single protein unit.

        A Plethora of Purposes

        What does a protein do? Let us count the ways. Really, that’s almost impossible because proteins do just about everything. Some of them tag things. Some of them destroy things. Some of them protect. Some mark cells as “self.” Some serve as structural materials, while others are highways or motors. They aid in communication, they operate as signaling molecules, they transfer molecules and cut them up, they interact with each other in complex, interrelated pathways to build things up and break things down. They regulate genes and package DNA, and they regulate and package each other.

        As described above, proteins are the final folded arrangement of a string of amino acids. One way we obtain these building blocks for the millions of proteins our bodies make is through our diet. You may hear about foods that are high in protein or people eating high-protein diets to build muscle. When we take in those proteins, we can break them apart and use the amino acids that make them up to build proteins of our own.

        Nucleic Acids

        How does a cell know which proteins to make? It has a code for building them, one that is especially guarded in a cellular vault in our cells called the nucleus. This code is deoxyribonucleic acid, or DNA. The cell makes a copy of this code and send it out to specialized structures that read it and build proteins based on what they read. As with any code, a typo–a mutation–can result in a message that doesn’t make as much sense. When the code gets changed, sometimes, the protein that the cell builds using that code will be changed, too.

        Biohazard!The names associated with nucleic acids can be confusing because they all start with nucle-. It may seem obvious or easy now, but a brain freeze on a test could mix you up. You need to fix in your mind that the shorter term (10 letters, four syllables), nucleotide, refers to the smaller molecule, the three-part building block. The longer term (12 characters, including the space, and five syllables), nucleic acid, which is inherent in the names DNA and RNA, designates the big, long molecule.

        DNA vs. RNA: A Matter of Structure

        DNA and its nucleic acid cousin, ribonucleic acid, or RNA, are both made of the same kinds of building blocks. These building blocks are called nucleotides. Each nucleotide consists of three parts: a sugar (ribose for RNA and deoxyribose for DNA), a phosphate, and a nitrogenous base. In DNA, every nucleotide has identical sugars and phosphates, and in RNA, the sugar and phosphate are also the same for every nucleotide.

        So what’s different? The nitrogenous bases. DNA has a set of four to use as its coding alphabet. These are the purines, adenine and guanine, and the pyrimidines, thymine and cytosine. The nucleotides are abbreviated by their initial letters as A, G, T, and C. From variations in the arrangement and number of these four molecules, all of the diversity of life arises. Just four different types of the nucleotide building blocks, and we have you, bacteria, wombats, and blue whales.

        RNA is also basic at its core, consisting of only four different nucleotides. In fact, it uses three of the same nitrogenous bases as DNA–A, G, and C–but it substitutes a base called uracil (U) where DNA uses thymine. Uracil is a pyrimidine.

        DNA vs. RNA: Function Wars

        An interesting thing about the nitrogenous bases of the nucleotides is that they pair with each other, using hydrogen bonds, in a predictable way. An adenine will almost always bond with a thymine in DNA or a uracil in RNA, and cytosine and guanine will almost always bond with each other. This pairing capacity allows the cell to use a sequence of DNA and build either a new DNA sequence, using the old one as a template, or build an RNA sequence to make a copy of the DNA.

        These two different uses of A-T/U and C-G base pairing serve two different purposes. DNA is copied into DNA usually when a cell is preparing to divide and needs two complete sets of DNA for the new cells. DNA is copied into RNA when the cell needs to send the code out of the vault so proteins can be built. The DNA stays safely where it belongs.

        RNA is really a nucleic acid jack-of-all-trades. It not only serves as the copy of the DNA but also is the main component of the two types of cellular workers that read that copy and build proteins from it. At one point in this process, the three types of RNA come together in protein assembly to make sure the job is done right.


         By Emily Willingham, DXS managing editor 
        This material originally appeared in similar form in Emily Willingham’s Complete Idiot’s Guide to College Biology

        We gotta watch out for feminine role models wearing pink

        Beware blonde, feminine role models wearing pink.
        (Source)

        Today’s guest post comes to us courtesy of Sara Callori. She is a physics Ph.D. candidate at Stony Brook University in Long Island, NY. In the lab, Sara loves working with x-rays and even has a Bragg diffraction tattoo. She would eventually like to focus on science teaching and outreach because she loves to get people to stop being intimidated when they think of physics.
        This may sound odd, but I never aspired to be feminine until I became a physicist. I grew up playing sports and getting short haircuts. There were phases when my mother would have had to tranquilize me to get me into a dress (this was infrequent as my tom-boy qualities seemed to come from her own lack of femininity). As I got older, I started to develop some style, but it was more comfort over fashion, especially when it came down to 8 am classes in undergrad. When I made the decision to go into graduate school for physics, however, my outlook changed. I wanted to be someone who bucked the stereotype: a fashionable, fun, young woman who also is a successful physicist. I thought that if I didn’t look like the stereotypical physicist, I could be someone that was a role model to younger students by demonstrating an alternative to the stereotype of who can be a scientist.
        This week researchers at the University of Michigan released findings that dashed my hopes for being the cool physicist that younger girls want to emulate. In a paper titled “My Fair Physicist? Feminine Math and Science Role Models Demotivate Young Girls”, psychology researchers Diana Betz and Denise Sekaquaptewa found that women presented as both successful in science/technology/engineering/math (STEM) careers and possessing “feminine traits” negatively affected how young girls viewed science and math.
        When I read the summary of these findings, I was dismayed. I became even more disappointed when I read that for feminine traits they used “wearing make-up and pink clothes, liking fashion magazines”. Gender-neutral women were given traits such as “wearing dark-colored clothes and glasses, likes reading”.
        The assignment of these traits bothered me on several levels. The most immediate was how narrow the study’s concept of “feminine” seemed. If you asked me if I considered myself feminine, I would say yes. I like colorful dresses during the summer and own too many purses — but I also wear glasses, play rugby, and have tattoos. Most real-life women, including women in STEM, also possess traits from a mix of “feminine” and “gender-neutral” categories. It is important to remember these are the women younger students will encounter when they are introduced to female scientists.  
        Additionally, the researchers’ idea of “feminine” seems to play into another set of negative stereotypes common in popular culture, what you might call the “Legally Blonde” scenario. In the movie, the protagonist is a woman who could easily be described as “wearing make-up and pink clothes, liking fashion magazines”. The story builds around how someone with those traits is perceived as unintelligent and unsuited for work that requires a strong academic background. While throughout the story, the main character shows she isn’t just a pretty face, there are still many people who will associate these types of feminine traits with unintelligence. 
        This association is at odds with women in STEM fields and it makes me wonder if some of the girls’ negative associations of feminine STEM professionals were due to those traits being perceived as incompatible with women in STEM careers. (To briefly address the finding which showed that femininity could be compatible with overall school success, the “success” descriptions seem to be generic enough that they could be interpreted as encompassing non-academic accomplishments as well; e.g. being well liked by classmates or elected to the student council.)
        This study also unsettled me on a personal level. I’ve long desired to be a role model to younger students. I enjoy sharing the excitement of physics, especially with those who might be turned away from the subject because of stereotypes or negative perceptions. I always thought that by being outgoing, fun, and yes, feminine would enable me to reach students who see physics as the domain of old white men. These results have me questioning myself, which can only hurt my outreach efforts by making me more self conscious about them. They make me wonder if I have to be disingenuous about who I am in order to avoid being seen as “too feminine” for physics.
        Overall, that this study could be useful as a springboard for improving discussion and ideas for motivating girls in STEM. However, I think that their idea of “feminine” is too narrow to apply these findings broadly. Rather than work in the black and white “feminine” vs. “gender neutral” cases, why not build further ideas, research, and programs around much more realistic types of women who are currently succeeding in many STEM fields.
        These views are the opinion of the author and do not necessarily either reflect or disagree with those of the
        DXS editorial team. 

        #DispatchesDNLee: Handling lady-business in the field

        An African-American woman and scientist in Tanzania

        by Danielle Lee, Ph.D.

        Actual field diary entry, Tuesday, August 7, 2012, ~8:30 am

        I cried this morning. In the shower. I was trying (poorly) to suppress screams of pain as I let the water run on my leg. I knew it was going to be bad when I saw blood on my pants as I pulled my field cover pants off. 

        I had been running into the same bush on line 3 between traps C and D every day. It has scraped me good, but this time it really hurt. I fell down and screamed in pain. Shabani* was breaking across the field to come to see about me. It really was of no use. He couldn’t help me. I just needed a minute or two to recover. I soon walked it off.

        But in that moment standing in the shower, I let out a yelp. I tried to hold my scraped leg under the hot water to clean the wound. But it stung like the devil.

        Lee_Legs_2057I cried, much like I did as little girl. I looked down at my scarred legs and immediately recollected the summer of 1981. I was such a tomboy, playing in the yard and in the streets with my boy cousins, and clumsy, so clumsy. My legs and arms were covered in bandages like tattoos. This obviously frustrated my bio-dad to no end. I vividly remember him threatening to spank me if I got another scratch on my legs. He scolded that I was a girl and I had no business being scarred up like that. I was shook. I tried to play more girl-like and carefully, but it was of no use. I liked climbing trees and tussling too much to stop. So I resorted to hiding my scars from him.

        But as I looked at my abused legs, I couldn’t help but think how ‘unlady-like’ my stems were. What boy is going like me with my legs looking like that or with feet badly needing a pedicure?

        And it makes me wonder, Do male researchers ever have conversations like these with themselves or with each other? Unlike our male counterparts, female researchers or long-term travelers and hikers have a few extra hygiene and grooming regimes to consider.

        What about that time of the month?

        How do I keep a happy lady garden in the middle of the bush?

        Do I or don’t I shave my legs?

        First, the monthly menses

        Dealing with the logistics of menses is always an inconvenience to me. My previous field research experiences taught me that tampons are the most wonderful invention, ever! They are especially handy if you have a heavier flow or will be busy for long periods of time in the field. Wear a pad for backup so as not to soil and permanently stain your good field pants. However, the last time I was in a developing nation doing field ecology, I said if I could halt my period for the time I was there, then I would certainly do it. I was able to do just that: I had a hysterectomy 3 years ago(yay for me), but am sorry I can’t offer more first-hand advice for managing menses to younger researchers. [Ed. note: Some birth control pill formulations promise to limit bleeding to four times a year.]

        I did make note that you can get feminine products in Tanzania, primarily sanitary napkins. They come in small-quantity packages, and there are not many varieties. It’s like the options that were available in 1980. If you have a preference for certain products, e.g., dry-weave, wings, long/short, light/super-absorbent variety pack, then I recommend bringing your own.

        Second, maintaining your lady-garden

        Since said hysterectomy, I have become more sensitive to microflora imbalance. It didn’t occur to me to be prepared for yeast infections. I eventually asked one of the other U.S female researchers if she had suffered from yeast infections since living in Tanzania. She told me that she had but that she was prepared. Her doctor pre-prescribed vaginal antifungals to take with her on her trip. I was not warned, but it occurred to me that if I was drinking bottled water because of the risks of local water disrupting my GI tract, then maybe my private parts would be sensitive as well. I began washing my sensitive areas with bottled water and noticed an immediate improvement. I also began taking acidophilus pills to get my system on track.

        But let’s not underestimate the importance of your clothes and underwear-cleaning regime. You may discover you are allergic to the washing powder sold and used there. If that is the case, then I recommend hand-washing your unmentionables with bar soap and hanging them up to air dry in a dust-free location.

        No matter what may be the root of your sensitivity (including old-fashioned stress), I highly recommend all female researchers to include vaginitis treatment ointments/creams and/or pills in your sundry first-aid and medicines kits. It is as important as packing anti-itch creams and anti-diarrheal pills in my book.

        Finally, to shave or not to shave?

        I have vanity issues, I admit. I (unnecessarily) obsess over grooming. Should I continue to shave my legs and underarms? Hirsute woman problems. The truth is, this grooming obsession didn’t matter. There was no need to obsessively attend to whiskers above my lip or on my chin or get a pedicure or even (welp) wear deodorant. Taking cues from local women, I noticed no one shaved their legs or under their arms – at least not as obsessively as we do in the West. And everyone had dusty feet! LOL, seriously red dust was everywhere and people wore sandals or flip flops or went barefoot for many occasions and traveled long distances, too!

        A week before my departure, I ran out of my solid, invisible unscented deodorant. I thought that I would just go to the drug store and buy more. Nope! I visited 4 stores and could only find was liquid roll-on anti-perspirant that was flowery smelling. It did nothing for me, but it didn’t really matter. It wasn’t uncommon to smell a ‘day’s worth of work’ on people throughout the day, but I felt uncomfortable.

        These were my obsessions. However, doing these are things made me feel human, like a woman even. But it was a relief to relax my obsessive pre-occupation with my body for a while.

        The take-home message is if there are some things that help you make it through the day or season, then bring them, e.g., tweezers, hand mirror, a pumice stone, or certain brand of hygiene product. Yes, most basic products are available at the local dukas or apothecaries, and prices are fair. However, the varieties are limited. There is no better way to be reminded of how first-world you are than when you ask for a single-use, fancy-pants, non-essential comfort-only products in a developing nation.

        *Shabani – Shabani Lutea was my field research assistant. He works for Sokoine University of Agriculture and is experienced trapping and handling wild African Pouched rats (without gloves!) He is the most awesome field research assistant there ever was, forever branded as the Rat Whisperer, because he really is that good.

        About the author

        DNLee is a post-doctoral researcher at Oklahoma State University. She is currently studying African-Pouched Rats, Cricetomys gambianus, an interesting yet largely mysterious animal that uses its keen sense of smell to detect landmines. She spent summer 2012 in Morogoro, Tanzania, studying the animals in the wild and in captivity. This is DNLee’s second installment in her series for Double X Science about her field experiences in Tanzania.

        Photo credit: All photos, courtesy of Danielle Lee, Ph.D. Continue reading

        Friday Roundup: 2011 top science lists, radium laced condoms, and the clitoris

        A Double X Science grandma showed us this picture.
        We thought it was the most ridiculously cute thing we’d seen all year.

        As 2011 draws to a close, media outlets and science bloggers have busily collated their top-10 (or 12 or 20) lists of science-related cool/interesting/freaky/fantastic stuff this year. Here’s a selection that should keep you busy for about the first half of 2012:

        Enjoy!


        Health ‘n’ stuff

        • Do you know the clitoris? Not many people really do. Read this. It’s important information, not to mention mindblowingly cool.
        • Put the toilet seat lid down when you flush. Please.
        • Emily Willingham, Double X Science managing editor, is also an editor on a new book just out, The Thinking Person’s Guide to Autism. Consider buying a copy to leave in your pediatrician’s office or to donate to your local library.
        • Once upon a time, people made condoms that glowed in the dark, thanks to radium. Yikes.

        Sciencey fun!