Category Archives: Biology GRE

Writings on the Biology GRE Subject Test

Amino Acids and DNA

Let’s do an easy one, shall we? Ok! Here’s the question:

The cDNA fragment that includes the ricin gene is 5.7 kilobases. If the entire fragment codes for the ricen polypeptide,the approximate number of amino acids in the poly peptide would be: (enter some weird numbers with lots of zeros here).

Well, once again the GRE just loves trying to confuse people with scary names and things. In this case, it throws in that whole ricin thing to throw you off. You can really just take that out of this question, so it reads something like “The cDNA fragment is 5.7 kilobases. How many amino acids does this code for?”

Alright, this is another one of those you-have-to-know-it questions. How much DNA does it take to code for a single amino acid? First, some very basic background. Amino acids are the building blocks of protein, and really what DNA codes for. Remember when we talked about DNA? DNA strands are studded with genes. Genes are simply lengths of DNA that code for certain proteins. Since the lengths of DNA make proteins, parts of the genes must code for the building blocks of proteins, or amino acids.

The next logical question is what percentage of each length of DNA codes for each amino acid? Ok, I’ll just tell you: 3 base pairs. Yep, that’s it. 3. Once you know how many base pairs are in a gene, then you just divide by three and that gives you the number of amino acids the gene codes for. How many base pairs are in the gene the question is asking about? 5.7 kilobases. Once again, don’t be afraid of words here. “Kilo” simply means 1000, while “bases” means, well, bases. So 5.7 kilobases is 5700 bases or base pairs. Divide that by three, and you get the nice round number of 1900. There you go!

Where do blood cells come from?

Well, conferences are over for the time being, so I’m now able to post daily once again. Here’s today’s question:

Exposure to high levels of radiation in humans has been demonstrated to cause anemia. The most likely explanation for this is that the radiation damages the: (and then it goes on to list some places).

Ok, this is a relatively simple question that tests your knowledge of some basic anatomy and physiology. First things first: I’ve noticed that these tests just love making questions seem more complex than they really are. Take this one, for example. The very first line talks about high levels of radiation. I don’t know about you, but I studied very little radiation in my biology classes, so when I first read the question, I got a bit worried about what I’m supposed to know. The question is misleadingly complex. If you just take out the radiation bits, you get a question that goes something like: “Damage to what part causes anemia?” That is much, much easier to answer! So I’m just going to skip the explanation about radiation and its dangers, and jump right into the meat of the question: what is anemia?

Anemia is a deficiency of hemoglobin or red blood cells. Hemoglobin deficiency lowers the blood cell’s ability to capture and transport oxygen throughout the body (bad, yes?) and a lowered red blood cell count causes basically the same thing. Either way, anemia is bad. Your tissues need oxygen, and the red blood cells are there to get it to them. Without red blood cells, you die. A lot.

Now, I’m sure some of you have been told you need to take iron to prevent or treat mild anemia. This is true, but don’t let it confuse you when you go to answer the question. Iron is a precursor to hemoglobin. The most common form of anemia is lack of hemoglobin, so taking iron supplements allows your body to produce more hemoglobin and therefore transport more oxygen. Lack of oxygen can cause lethargy, hence the tired feeling associated with anemia.

This question, however, is referring to the other form of anemia: lack of red blood cells. How do I know? I looked at the answer list! Here’s the question again (this time with the answer list present):

Exposure to high levels of radiation in humans has been demonstrated to cause anemia. The most likely explanation for this is that the radiation damages the:
A) Blood vessels
B) Spleen
C) Liver
D) Thymus
E) Bone marrow

I advocate answering the question before you look at the answers, but sometimes the first answer you come up with isn’t listed. Here was my thought process as I read this question: “Well, anemia is caused by lack of hemoglobin or red blood cells, so radiation must attack the red blood cells themselves.” As you can see, this answer isn’t listed. If your top answer isn’t there, go through the rest of the answers and see which one makes the most sense.

Blood vessels. While damage to the blood vessels could cause blood leakage into various body cavities and eventually cause anemia due to lack of blood cells circulating, anemia isn’t the first worry. I would be much more worried about internal bleeding, which would probably present as pain or death. Tiny amounts of internal bleeding may cause anemia, but that would mean only tiny amounts of radiation damage, and that isn’t likely unless the radiation was controlled in some way (as in radiation therapy). I disregard this one right off the bat.

Spleen. Anyone who has studied the circulatory system knows that the spleen is involved. The spleen filters worn out red blood cells and sends them to the liver for processing. It also holds a small amount of blood in reserve for times when you need that extra burst of oxygen–like exercising or hiking at high altitudes. This makes your blood system more efficient. However, you can live without this little extra burst without any ill effects. Lacking a spleen doesn’t cause anemia. It just like living without a savings account–not the most comfortable way to live, but it doesn’t mean your checking account has any less money than it would have otherwise.

Liver. The liver does bunches and bunches of things that you don’t need to know about at the moment. One major job is the break down of red blood cells and the recycling of hemoglobin. The liver breaks down the worn out red blood cells and gets rid of the excess material via billirubin. Liver damage would cause major problems in a person, but wouldn’t cause anemia.

Thymus. The thymus gland is a place where certain white blood cells go to mature. Don’t worry, I’m sure there’s a question about white blood cells coming up that I can use to address this issue. Just know that it doesn’t cause anemia.

Bone marrow. Ah, we’ve found it. Bone marrow is what gives rise to all the blood cells circulating in your blood stream. Immature blood cells are formed in the bone marrow, then travel to a variety of places to mature. If the bone marrow gets damaged, it no longer can produce blood cells, which will result in a lowered red blood cell count and eventually anemia. Going back to that bank account example, while the spleen is like your savings account, the bone marrow is like your job. While you can live just fine without a stash of money somewhere, if your income gets cut off then your screwed. Bank account anemia!

So, the answer to this question is “E” bone marrow. Yay!

How DNA moves through a electrophoretic gel



Well, I’m sitting at a conference at the moment, and have decided that it has been too long since I have indulged in the joy of biological teaching. Seriously! Stop laughing. Here’s the question I randomly chose for today:

The rate at which a DNA fragment moves in an electrophoretic gel is primarily a function of the fragment’s….

Isn’t it lucky that I totally by accident chose a question that can be answered pretty quickly? I know! Lucky! Anyhow, let me tell you a little about electrophoresis. This process is a step used in laboratories to study DNA, and is often taught in every single lab class in college simply because it’s rather simple and rather impressive. (Seriously–try this the next time you’re having dinner with your family “So I was studying deoxyribonucleic acid the other day, and needed to separate the fragments after I broke the bonds at known gene sites, so I simply ran an electrophoretic gel.” This is good for at least an extra helping of dessert and hours of proud bragging by your mom at the next knitting circle).

Well, how exactly does this work? DNA, as you might imagine, is huge. Think about the amazinhg amount of information stored in the genetic code–all that information just sitting there waiting to be expressed. When we study DNA, we usually want to study a particular section, or a particular gene. We do this by cutting the big string of DNA into fragments using enzymes. We then copy the DNA (lots and lots and lots through PCR which I’ll explain in a later post) and then somehow have to pick out the genes we want to focus upon.

This is where electrophoresis comes in. An electrophoretic gel is basically really stiff Jell-O. The gel is melted and poured into a rectangular mold, and 8 (or so) wells are formed in one end of the solidified gel. These wells give us a place to put the DNA. Now, DNA has a charge. Due to it’s chemical make up and all that jazz, it has a an overall negative charge. At this point, we want to separate the DNA into its different fragments, so some smarty somewhere decided to use that overall negative charge to do just this. The gel (with its wells filled to the brim with DNA in a liquid medium) is subjected to an electrical current. The DNA fragments are pulled through the pores of the gel as it is attracted to the positively charged energy at the far end of the gel.

Now, the DNA separates depending upon its size. The bigger the DNA fragment, the harder it is to force it through those tiny, tiny pores in the solid gel. Therefore, the bigger (or longer) the DNA fragment, the more slowly it moves through the gel. After a predetermined amount of time, the electrical current is removed, and the gel is stained with some horrible substance that causes DNA to glow under a black light. You then take a picture of the gel and look at the bands (see the picture above) and the ones that are furthest away from the wells are the shortest, while the ones closest to the wells are the longest.

So, back to the question:

The rate at which a DNA fragment moves in an electrophoretic gel is primarily a function of the fragment’s:
A) Length
B) double helical structure
C) Radioactivity
D) Degree of methylation
E) Adenine content

Can you pick out the correct answer now? Movement through an electrophoretic gel is strictly due to size, therefore the answer is “A.”

I’m out of town for a bit….

So I’m out of town. I volunteered to be a delegate at annual conference this year, which means at the moment I’m lying in a rather musty-smelling hotel room in beautiful downtown San Bernardino, and I have to be up in a minute to go to a variety of boring meetings and vote on matters that may or may not affect me and those I care about. Oh, and it’s also a thousand degrees outside. I will do what I can to get a post up, but this will be sporadic until I make it home on Sunday. Don’t miss me too much!

Plant hormones

I think I’m going to be moving into the plant phase of this blog. You see, a certain percentage of the GRE involves botany (they say it’s only 15-33%, but it seems like a lot more on one of the tests I am looking at). Also, in the next few week’s I’ll be running a week-long training for grade school teachers in botany, so I need to brush up on my skills. Here we go:

Today’s question:

Which of the following plant hormones hastens apple ripening?
A) Auxin
B) Gibberellin
C) Abscisic acid
D) Cytokinin
E) Ethylene

Let’s dissect the question. What exactly is a hormone? A hormone, in terms of this question, is any of a handful of plant compounds that control the growth and differentiation of plant tissues. Basically, hormones control lots of things having to do with plant growth and development.

This question entirely depends upon your knowledge of plant hormones. There’s not really a good way to guess your way through this one, which makes it a bit of a pain in the ass. Get your flash cards ready! Let’s go through the hormones.

Auxin: Auxin has to do with the growth of plant tissues. Anyone who has ever grown plants know they have a neat tendency to do things like grow towards the light, and the stems grow away from gravity while the roots grow down. (Oh! Try this: take a plant you have in a pot and place it on its side. After several days, the stem will bend so it is once again growing away from gravity. You can also put a plant in a dark room with one window, or in a box with a window cut in the end. After a few days, the stem will bend towards the light source, and the plant will start growing towards the light.) So what happens in these two situations? Well, plant cells have auxin in them. When light hits the tip (or growing center) of the plant from one side, then the auxin present on that side flees from the light (maybe it’s a vampire?) and concentrates on the other side of the cell. This causes the illuminated side of the plant to grow more slowly than the dark side. This over zealousness makes the plant tip grow towards the light, which allows the plant to get as much light energy as possible. The same basic thing happens with gravity. The auxin in root cells drop to the lowest point of the cell, which causes that tissue to grow faster than the higher points. Make sense? Of course it does. It all breaks down to this: auxin makes tissue goes faster. Wherever there’s a lot of it, that’s what grows.

Gibberellin: Giberellin is also in charge of growth, but in a different way than auxin. Gibberellin takes care of stem growth upwards, as opposed to which way the plant grows. This hormone is in charge of making stems grow tall really, really quickly, especially in those plants that are usually short. (Hey, when do you think this would happen? Perhaps in plants that are trying to compete for sunlight and need to outgrow their competition. Hmm.) It is also in charge of inhibiting new root formation, and stimulating new phloem cells. We’ll talk about the xylem and phloem in another post. They are rant worthy, that’s for sure. Finally, giberellin break the dormancy of buds and seeds and start the flowering in some plants during their first year of life.

Abscisic acid: Abscisic acid is in charge of stopping cell growth. This primarily happens when a plant needs to go dormant to avoid damage from excessive cold. This is what causes all the trees to stop growing during the winter and whatnot.

Cytokinin: All these hormones seem to govern plant growth, don’t they? Cytokinin is no different–this particular hormone causes cell division. It also has a neato interaction with auxin: in undifferentiated cells, the ratio of auxin and cytokinin becomes very important. If auxin is dominant, the cells turn into root cells. If cytokinin is dominant, then the cells turn into stem and eventually bud cells. Ah, the webs these hormones weave!

Ethylene: Ethylene seems to be the only hormone that doesn’t govern growth of tissues. This hormone travels through the air–noticed that all the other hormones stick to the tissues. This stuff goes everywhere. Ethylene is in charge of ripening fruit and the loss of leaves during the change of seasons. Have you ever heard of putting unripened fruit in a bag with half an apple? When fruit gets damaged or ripe, it gives off ethylene. Ethylene causes ripening, so putting a sliced apple with some unripened fruit causes the unripened fruit to ripen quickly. This is also why you don’t want bruised or over ripened fruit with fruit you don’t want to ripen too quickly–the ethylene will cause everything to ripen right up.

Now that we know everything there is to know about these five hormones, back to our question:

Which of the following plant hormones hastens apple ripening?

A) Auxin
B) Gibberellin
C) Abscisic acid
D) Cytokinin
E) Ethylene

Since we know that the first four are in charge of tissue growth, that leaves ethylene as our answer. Yay!

DNA Replication (i.e. Base Pair Porn!)


Could I come up with a more boring title? I don’t think so! But how in the world do you write something interesting about how DNA copies itself? Maybe “base pair porn!” That would totally work! I’m putting that now…hee for me! Anyhow, on to today’s question!

When DNA replicates semi conservatively, which of the following is true of each daughter DNA molecule?

A) Both strands are newly synthesized
B) One strand is newly synthesized, whereas the other is a strand from the parent DNA molecule
C) Both strands are the original strands of the parent molecule
D) One strand has more AT-rich regions than the other strand has
E) The newly synthesized strands are more susceptible to melting and renaturation than the parental DNA strands are

Ok, the big question in this question is “What is semi conservative replication?”

Remember that blog I did about complimentary base pairing? Yeah, me too! That was a good one. Sigh. Well, this is sort of a continuation of that last post. When DNA needs to copy itself, it undergoes replication. There are three methods the books talk about when discussing DNA replication: conservative, dispersive, and semi conservative.

Conservative DNA replication is when an entirely new double helix of DNA is replicated for the new (or daughter) cell. This works just like a copy machine–it’s based on the mother cell’s dna, and an exact copy is made. The two new strands are what are sent on to the daughter cell, while the strands they were copied from are left in the mother cell. This method of DNA replication has not been found to be biologically significant, so most people don’t really care about it. And neither do we!

Dispersive replication is when bits and pieces of the mother strands are mixed up with new sections and all put together into a new double helix. The two daughter cells end up with a strange mix-and-match version of the DNA made up of both mother and daughter sections. Just like the last one, no one thinks this is a biologically significant method of replication.

Finally, the big one: semiconservative replication. This is the main way DNA is totally replicated during cell division. During this type of replication, the entire DNA double helix unzips. A new strand is made to match up with each original strand using complimentary base pairing. The result is two double helices where only one was before. Each double helix is made up of an old strand of DNA (the mother strand) and a new strand of DNA (the daughter strand). Each new daughter cell gets a double helix of DNA–one strand from the mother cell and one brand-spankin’-new strand. This is the only replication method of the three that is considered biologically significant (meaning, this is what we care about!)

Ok, back to the question:

When DNA replicates semi conservatively, which of the following is true of each daughter DNA molecule?

A) Both strands are newly synthesized
B) One strand is newly synthesized, whereas the other is a strand from the parent DNA molecule
C) Both strands are the original strands of the parent molecule
D) One strand has more AT-rich regions than the other strand has
E) The newly synthesized strands are more susceptible to melting and renaturation than the parental DNA strands are

Let’s go through the answers. “A” is obviously incorrect, since we just learned that when both strands of a double helix are newly synthesized, that is called conservative replication. “C” is also wrong, because if both strands were of the parent molecule, no replication would have happened at all….the DNA would have just moved from one cell to another. “D” just doesn’t make much sense. We know from complimentary base pairing, that each strand has exactly the same number of bases, so it’s impossible for a semi conservatively replicated strand to have more AT regions than the other. “E” tries to throw you off by mentioning melting and renaturation, but we don’t care about that.That leaves “B.” This answer is the definition of semiconservative replication–one strand is newly synthesized, whereas the other is a strand from the parent DNA molecule.

There you go! Yay us!

The lytic viral cycle

Welcome to post #2 about viruses! Remember the last one? During that post I told you about how viruses are the underdog of the living world (being that no one knows if they are actually living or not), and are composed soley of a protein coat and an inner genome. Today’s question revolves around the cycle of infection the virus undergoes in order to initiate reproduction:

Successful reproduction of a lytic virus requires that all of the following processes occur EXCEPT

A) incorporation of viral DNA into host cell DNA
B) translation of viral mRNA
C) binding of the virus to the host cell’s surface
D) penetration of the viral genome into the host cell
E) replication of the viral genome

First off, there are two types of cycles that viruses can undergo to take over a cell: they lytic and the lysogenic cycle. The lysogenic cycle is interesting; during this cycle, the viral DNA is integrated into the host cell’s DNA for an indefinite period of time. Basically, the viral DNA just moves in and lives in a new cell until it wants a change of scene. This may be in a day, or it may be in 1000 years…there’s no real way to tell from our perspective.

The question we’re worried about today involves that other cycle–the lytic cycle. During the lytic cycle, the virus takes over a host cell, utilizes the host cell’s ability to make ATP, then bursts the cell open. This doesn’t take long at all. The lytic cycle has four major stages: Adsorption, Penetration, Biosynthesis of viral products, and Release.

The viral cell is formed kinda like a hypodermic needle. The virus comes across an appropriate host cell (due to the intimacy of viral reproduction, viral cells are closely matched with their host cells. This is why most animal viruses can’t jump from species to species, and when they do it is due to a massive mutation) and attaches to proteins found on the host cell’s membrane. This adsorption period takes a bit of time and usually requires a slightly elevated temperature to happen effectively.

Once the virus is attached to the outside of the host cell, it then injects its genome into the host cell. Can you guess what this stage of the cycle is called? Yup. Penetration. The protein coat is left on the outside of the cell while the DNA/RNA of the virus does its dirty work inside.

The viral DNA must then figure out how to take over the cell (it’s like an evil mastermind!). So, it follows normal DNA replication protocol–first it unzips, and then it translates messenger RNA to send a memo to the cell saying ‘Hey! Replicate me!” Which the cell does, no questions asked. Silly minions!

Once that memo gets sent, the cell stops what it was doing, and begins to synthesize the viral products during the “biosynthesis of viral products” phase. The cell reproduces new, baby viruses until all the ATP and other cell resources are gone, and the cell is just PACKED full of new viruses waiting for the chance to infect a cell of their very own.

After the host cell is tapped out–oh you viruses! It’s all wham bam thank you host cell–then the host cell bursts open, releasing all the viralings into the big bad world. Release!

So, four major stages in the lytic cycle. Now, back to our question:

Successful reproduction of a lytic virus requires that all of the following processes occur EXCEPT

A) incorporation of viral DNA into host cell DNA
B) translation of viral mRNA
C) binding of the virus to the host cell’s surface
D) penetration of the viral genome into the host cell
E) replication of the viral genome

This question is testing your knowledge of the lytic cycle and its differences with the lysogenic cycle. We just learned the 4 stages of the lytic cycle: Adsorption, penetration, biosynthesis, and release. Looking at the 5 answers to this question, which one isn’t included in those 4 stages? Translation of viral mRNA is the first step in biosynthesis; binding of the virus to the host cell’s surface is the definition of adsorption; penetration of the viral genome into the host cell actually has the word “penetration” right in the answer; and replication of the viral genome is just another way of saying biosynthesis (it’s just that biosynthesis sounds more sciencey, so I teach my students to use that word. Impress your friends and family!) The only answer that is not included in the four stages is “A”, incorporation of viral DNA into the host cell DNA. Remember that this is the hallmark of the lysogenic cycle–where the viral DNA is incorporated into the host cell’s DNA for an indefinite amount of time. Answer: A!

Saccharmoyces cerevisiae and sex

Ah, yeast. That beautiful, single-celled organism that gives us so much good stuff–mmm…beer. Well, at them moment, the GRE doesn’t seem to care about the goodness of alcohol. Instead, it cares more about the taxonomical groupings of the yeast responsible for some many drunken hookups–Saccharomyces cerevisiae.

Here’s the question:

The yeast Saccharomyces cerevisiae is classified as belonging to which of the following groups?

A) Eubacteria
B) Oomycota
C) Zygomycota
D) Ascomycota
E) Basidiomycota

Scientists like grouping like things together. We don’t like having all these uncategorized species just lying around all on their own. Who do they think they are?!? Anyhow, S. cerevisiae is a yeast. Yeasts are a type of fungus, and are grouped together with all those fungi you know and love–mushrooms and molds. Members of the fungal group are put together by their method of sexual reproduction.

Ok, so fungi reproduce by producing spores–hardy, thick walled thingys that can survive most any horrible thing. Most molds reproduce most of the time asexually. This takes less effort and energy than sexual reproduction, so it tends to be the go-to option for most species. When times get rough, however, almost all of the species resort to sex to make sure their offspring have a good chance of survival.

So, what “groups” do fungi fall into? There are 6 major fungal groups (specifically, they are phyla): Chytridiomycota, Oomycota, Zygomycota, Ascomycota, Deutromycota, and Basidiomycota. Notice that all the fungal groups end in -mycota (that’s a big clue to this question). The Chytrids are ancient molds, mostly aquatic, and super interesting to other people. The big representative of this group is Allomyces.

The second group is Oomycota, which are filamentous, water and downy mildew molds. As all of you who know a little bit about beer and bread, S. cerevisiae is a single celled organism, so it doesn’t fall into Oomycota.

The final three groups are the higher fungal groups, and our best bet for S. cerevisiae. Organisms in Zygomycota produce zygospores; those in Ascomycota produce ascospores within an ascus; Basidiomycota members produce basidiospores; and organisms in Deutromycota don’t have any known sexual cycle. Granted, that last group is just a catch-all for all the organisms we’ve discovered that we can’t make do it in the lab.

Well, what do S. cerevisiae do? They produce ascospores within an ascus. I really don’t have a good way of helping you remember this–maybe just straight memorization here? Sorry!

So, back to our question:

The yeast Saccharomyces cerevisiae is classified as belonging to which of the following groups?

A) Eubacteria
B) Oomycota
C) Zygomycota
D) Ascomycota
E) Basidiomycota

As we now know, Saccharomyces cerevisiae belongs to Ascomycota. Yay!

Viruses and ATP

The past couple of posts have been about human anatomy and physiology (which is what I’m currently teaching at SJSU) so I decided to branch out just a tiny bit in today’s post–today I’m going to give a brief introduction to viruses. Here’s today’s question:

Members of which of the following groups CANNOT produce their own ATP?

A) Lichens
B) Bacteria
C) Viruses
D) Diatoms
E) Protozoa

This question is testing two things: your knowledge of vocabulary and your knowledge of organismal groups. First off, the vocab. ATP is the big work in this question. ATP stands for Adenosine Triphospate, and is the energy source for cells (well, it’s quite a bit more complex than that, but I’m not going to go into it here. If you would like a very, very in depth discussion on the chemical basis of ATP and its exact function, do a search on Wikipedia. The ATP article there is fabulous). All cells use ATP to carry out essential functions such as growth, repair, and reproduction. Most organisms produce their own ATP–they have to, or they die. So, which of the above groups doesn’t? Let’s look at the groups and what they are.

Lichens: Lichens are symbiotic associations of (usually) an algae and a fungus. Without getting into the varieties of lichens, or the controversy on their relationship, the particular algae and fungus cannot live alone. However, once together the lichen is able to live, grow, and reproduce all on its own, and therefore produces its own ATP.

Bacteria: Bacteria are microscopic, single celled (for the most part) organisms. These are considered one of the smallest free-living organisms we know about. Bacteria have the ability to function apart from any other organism, although many thrive when in a symbiotic or parasitic relationship with something else. Bacteria produce their own ATP.

Diatoms: Diatoms are algae with cells walls made of silica (ever heard of diatomaceous earth? Yep, that’s these guys). Being algae, these singe celled organisms are able to live freely, and do so in bodies of water. A certain type of diatoms is what is responsible for red tide. Neat! Anyhow, since they are able to live freely, they produce their own ATP.

Protozoa: Protozoa are single celled, eukaryotic (have a membrane bound nucleus) organisms that are, for the most part, motile. They are much larger than bacteria, and differ in many other ways that I won’t get into here. Once again, however, single celled organisms capable of moving/growing/reproducing without other organisms, so they must produce their own ATP.

Viruses: Ah, viruses. Viruses are the bane of many a biologist. There have been whole summits on if a virus is alive or not, and the latest answer to come from the top minds in the field is “um…dunno.” Viruses simple beasts–they consists solely of a protein coat and an inner genome (either DNA or RNA, but not both) and are unable to carry out basic processes such as growth or reproduction without the assistance of another cell. This is where the controversy comes in–if they are unable to grow and reproduce on their own, are they really alive? Well, that’s neither here nor there for the moment. What we’re worried about is how viruses work. Viruses must hijack another cell and take over its ATP producing capabilities in order to do anything. It does this by injecting its genome into the host cell’s genome, and telling the host cell what to do from there. The host cell is sometimes destroyed during this process, and the virus goes on to infect another host.

So, the answer we’re looking for is “C” virus. Viruses must hijack another cell for basic functions, and therfore don’t produce their own ATP.

Quick morning note! Awesome story!

A Canadian newspaper is reporting a case of dark green blood in a surgery patient. I know! How neat is that?!?

Alight, this is a perfect opportunity to give a quick lesson on analyzing the things you read. This is basically an assignment I give in my Human Biology classes–especially if a really interesting story (like one about a guy with green blood!!) comes out in the news. How can you tell if a story you read or hear about is actually credible?

Step 1: Consider the source. I first heard about this story during my morning perusal of Boing Boing , one of my favorite sites for interesting and strange bits of non-news. Now, as much as I love these guys, I don’t consider them a totally credible source. They are, after all, a blog that reads internet sources and passes on the most interesting bits to me. Don’t get me wrong–when I say I don’t consider them credible I don’t mean I don’t read their work with a stalker-like fervor then instantly look up more information on the best parts. Nope, that’s exactly what I do. What I mean about “not credible” is I wouldn’t source boingboing.net in my next publication, or quote their words as fact without doing some extra research.

Source of information is very, very important when determining if a bit of information is credible. What is the author’s credentials? Where is the work published? Most scientists are very proud of their background and work, so they will announce it to the world. It shouldn’t be too hard to figure out if the person knows what they are talking about. (Quick hint: most general journalists, yes, even those who work for NPR, have a very basic knowledge of science and biology, and routinely make glaring errors in articles. Make sure you double check the facts!) Make sure the information is published somewhere where the author knows what he is talking about. This can be pretty much assured if the information is published in a journal that is peer reviewed, meaning other scientists with the same basic knowledge as the author have read the author’s work and have agreed with the facts and conclusions.

Most scientific journals are peer reviewed, and are therefore considered credible sources. If you read an article that mentions the information was published in some big peer reviewed journal (like the Lancet), go and read the original article to make sure the site your reading just didn’t make stuff up (which they do, sometimes). Which brings us to:

Step 2: Make sure the information is real. Because many journalists and bloggers are not scientists, they can easily misread information in a credible source, or misunderstand conclusions. If you read a part of an article that just doesn’t make sense to you, look up the facts. You’d be surprised how many basic journalists seem to forget they can just pick up a high school bio book. Now, just because a writer gets some information wrong doesn’t mean the entire article should be discarded. Most of the time the premise is correct; it’s just the details that don’t work. Look up the information and see what’s what. Enjoy the green blood article and tell your friends!