Protein Synthesis & Taco Bar Activity

Objective: You will apply your knowledge of the Central Dogma, protein synthesis and the genetic code to “synthesize” the perfect taco.

Part 1.

Directions:Using the information provided, complete the chart below using a codon chart or codon wheel.


DNA Triplet mRNA Codon Amino Acid
GGG CCC Proline

Part 2.

Directions: Genes contain the “recipe” for building proteins. Create your own taco recipe using the ingredients below. List your preferred ingredients (include a minimum of six unique ingredients) in the first column below and fill in the table accordingly. Don’t see your favorite listed? Create your own codon for your preferred taco ingredient. Don’t forget the start and stop codons!


Taco ingredients in codons:

UAC-Softshell             UGG-Beef                   CGU-Olives                UAU-Sour Cream

AUC-Hard-shell          CAA-Chicken              AGA-Jalapenos          CUA-Queso

GGA-Beans                CCC-Lettuce               AAC-Guacamole        CAG-Cheese

UCU-Fish                    ACC-Tomatoes           GUC-Salsa


Taco Ingredient DNA Triplet mRNA Codon Amino Acid
(stop)     (stop)


GMOs: Genetically Modified Organisms.  See also: Genetically Engineered (GE) organisms.  A GMO is created by inserting a piece of foreign DNA (genetic information, e.g. a gene) into another organism.

There is an enormous amount of information, misinformation and passionate propaganda covering this topic.  Perhaps, you’ve seen it popping up on your social media feeds.  If you’re just getting started – wading into this deep sea of GMO news – I highly suggest watching this piece from CBS Sunday Morning.  It will be 10 minutes well spent.

More commentary on this topic coming soon.

If you’re asking yourself: “What is a stink bug?”… you really don’t want to know.  Many regions in the United States have been inundated with the brown marmorated stink bug (BMSB, Halyomorpha halys), especially those of the mid-Atlantic where populations are highest.  Originally from Asia, these invasive insects are a nuisance as they enter homes (frequently during the fall months when temperatures begin to drop) and emit a pungent smell when crushed.

Agriculturally speaking, BMSB is a major problem rather than a nuisance.  On apples, BMSB feeding injures the fruit causing unsightly lesions, rendering it unmarketable (although it could still be processed for cider).  In 2011, BMSB cost Mid-Atlantic apple growers approximately $37 million in losses.  At this point, insecticides are the primary tool to manage BMSB on apple.  SMSB is also a pest of corn and soybeans, peaches, beans, citrus and ornamentals.

Now there is word of another newly introduced species of stink bug, the kudzu bug (Megacopta cribraria) headed toward the mid-Atlantic.  The first report of the kudzu bug came from Georgia in 2009 (BMSB was first spotted in PA in the 1990s) and it has been making its way north ever since.  It feeds on kudzu, an invasive plant abundant in the southern U.S. but also feeds on many other economically important species of bean (think: soybean and other garden varieties).  Weekly insecticide sprays may be required in an agricultural setting and homeowners can also spray an insecticide on vegetation surrounding their home to keep the insects at bay.

BMSB versus Kudzu Bug

The University of Georgia also reports that when crushed the kudzu bug emits an unpleasant odor (similar to the BMSB), can stain human skin and other surfaces and cause a minor allergic reaction (swelling/itchiness) on human skin.  Since insecticides should not be applied inside a home and a fly swatter is not an attractive option for the reasons listed above, experts suggest collecting the insects with a vacuum and killing them in soapy water.

As of fall 2013, the kudzu bug has been detected as far north as Maryland.  If the BMSB can over-winter in the Mid-Atlantic, there’s a good chance the related kudzu bug can too.  Next year keep your eyes peeled for both species in the garden.

Watch a WPXI Pittsburgh report on the kudzu bug here.

University of Georgia’s

Mycotoxins are small compounds found contaminating several plant products.  They are toxic to animals and humans in small doses and poisonings are often difficult to diagnose.  Symptoms of many mycotoxicoses are similar to each other and to those of other food poisonings and viral or bacterial diseases.

The story of aflatoxin, the first described mycotoxin, begins around 1960 in the United Kingdom.  A mysterious disease was running rampant through poultry farms, leaving upwards of 100,000 turkeys dead.  Veterinarians could not easily diagnose this new affliction labeled “Turkey X Disease”.  After ruling out known parasites, focus shifted to a common food source – a Brazilian peanut meal. The peanuts were found to be contaminated with a toxin they dubbed aflatoxin after the fungus found to produce it, Aspergillus flavus.

Aspergillus flavus fungus colonizing field corn (image: Maize Breeding Program at TAMU)

Aspergillus flavus fungus colonizing field corn (image: Maize Breeding Program at TAMU)

A. flavus colonizes oil-rich seeds, such as peanuts, maize (corn), cotton, ground nuts and pistachios.  Unlike many fungi, A. flavus and aflatoxin production are favored by hot and dry conditions.  In the United States, aflatoxin is a sporadic concern primarily for pets and livestock who consume corn and cottonseed products (See: 2006 and 2010 outbreaks in dry pet food).  However, it is a serious concern for human health in other parts of the world, most notably Kenya.  Highly toxigenic (produce high levels of aflatoxin) strains of A. flavus are native to regions in Kenya.  This combined with a maize-based diet and poor storage facilities (A. flavus can continue to grow and produce more aflatoxin after harvest if the grain is not kept dry) leads to aflatoxin poisonings every year in Kenya (even if they aren’t reported).  Aside from acute poisonings (involving liver failure and death), chronic exposure to aflatoxin can lead to liver cancer, jaundice, weight loss and immune system problems.  Aflatoxin can also pass from mother to baby through breast milk.  2004 marked the worst reported aflatoxicosis outbreak in Kenya and the world with 125 documented deaths.

A maize flour mill in Kenya (image: CDC).

A maize flour mill in Kenya (image: CDC).

What can be done?  Researchers have been focusing on understanding the populations of A. flavus in Kenya.  Atoxigenic (naturally produces no aflatoxin) strains of A. flavus have been identified and are being used as a biological control (A product called “aflasafe”) against more toxin strains.  The goal is for the toxin-free strains to outcompete the poison-producing ones in the maize fields, resulting in a less contaminated crop.  Extension and outreach programs have emphasized aflatoxin awareness for those who grow (management strategies, including the new bio control), store (keep it dry, inspect the grain) and sell maize (inspect before sale and production).

Please take a look at this slide show on aflatoxin management in Kenya.

Up next in this series, I’d like to discuss quantitative and qualitative testing methods for mycotoxins.  Testing is easier said than done (accurately), especially in a field setting.

Time to get back on track with our popular science updates.  These two stories peaked my interest this week:

Scientific American’s Agriculture and Innovation

This slide show gives us a peek at agricultural tools used 150 years ago when more than half of the U.S. population lived on a farm.  Some inventions border on absurd (like the combination sheep feeder and shearing table), while others are predecessors for modern tilling and harvesting machinery.  I think the drawings (all featured in issues of Scientific American from 1863) are works of art themselves.

Scientific American 1863 InnovationPhoto credit: Scientific American

Rare Flower Smells “like a dead rat in the wall”

Wait, this is news?  It is when the plant is rare and rarely flowers in nature, let alone in a cultivated setting (once every 7 to 10 years if you’re lucky).  The Amorphophallus titanum (The Titan Arum), commonly known as the corpse flower due to its unique fragrance, is part of the teaching collection at UC Santa Barbara.  This specimen, dubbed “Chanel”, bloomed July 31 and the sulfurous odor could be experienced throughout campus. The smell is attracts pollinators such as flies but a flower as rare as this attracted other guests of the human variety, as seen in this live feed.  To promote successful pollination, pollen was brought in from another A. titanum, which happened to flower the week prior at the U.S. Botanic Garden in Washington DC.  Good timing!

UCSB Titan AramPhoto Credit: Julie Cohen

PS – A video of a Titan Arum that bloomed in 2006 at the Brooklyn Botanic Garden, including time-lapse photography.

What have you been reading this week?


Welcome back to our Mycotoxin Series!

With wheat harvest mostly complete for the eastern United States, it only seems fitting that I write about deoxynivalenol (DON).  DON is produced by Fusarium graminearum (amongst others) and can be found in products made with wheat, barley and corn.  DON has been dubbed the “most commonly encountered” mycotoxin.  This is likely due to our diets (wheat and corn are staple crops in many cultures and are used in many food products) and much of the wheat we grow is rather susceptible to F. graminearum.

 FHB wheat head katelynwillyerd

F. graminearum is the causal agent of Fusarium head blight of small grains (also known as Scab).  The disease is characterized by premature “bleaching” of the wheat heads (see above), shriveled kernels, reduced yield and DON contamination.  F. graminearum also causes a disease in corn called Gibberella ear rot (more of a concern for livestock).  DON serves as a virulence factor for F. graminearum which means DON is a powerful “weapon” for this pathogen as it infects the plant.

DON is a mycotoxin that is harmful to both plants and animals (any eukaryotic cell, for that matter).  DON binds to ribosomes, preventing cells from translating genes to proteins (remember, Bio 101: DNA –> mRNA –> amino acids/proteins).  Without essential proteins, cells are unable to carryout basic function and die (e.g. bleached, dead tissue on wheat heads).

DON is also known as “vomitoxin”.  This gives you a pretty specific idea about what sort of symptoms we observe in humans and animals suffering from DON poisoning.  DON may also cause other gastro-intestinal distress, poor nutrient absorption, reduced weight gain, feed refusal and impaired immunity.  Despite being the most commonly encountered mycotoxin, we don’t have a good handle on the effects of chronic exposure to low doses of DON that may be in our breakfast cereals, breads, pretzels, pastas, etc.

DON facts katelynwillyerd

PS – A fact sheet I co-wrote on DON in corn in Ohio

…pick me a snake berry?!  More on that below…

I’m a big proponent of eating seasonally, primarily eating what’s ripe when it’s ripe and avoiding what isn’t ripe or “in season”.  Maybe it comes from growing up on an apple farm.  I just can’t bring myself to buy apples from a store in the spring because I know they won’t be as good as the fresh fall apples I remember.  Summer berries have an especially short window, and right now wild black raspberries are in season on our farm.


Rubus occidentalis is native to eastern North America and one of the most common Rubus species yet is not typically planted.


Botany Lesson: Like all raspberries, the fruits are multiples of drupes.  A drupe is a seed surrounded by a fleshy outer tissue.  A raspberry is an aggregate of many druplets, hence containing many seeds.  A peach, for example, is a single drupe: It contains one seed/pit and is surrounded by the part that we eat.  In nature, animals are attracted to this fleshy tissue and help with the dispersal of the seeds as they consume or transport them.


Admittedly, the wild black raspberries are more “seedy” and smaller than cultivated varieties, but they are still great on cereal or ice cream (or by the handful).  Not to mention free, “organic”, and you never know when you might see a snake slither out of the bramble…  Unfortunately, I did NOT get a photo as I was more concerned with keeping my dog away.  It was most likely a black rat snake, and easily the longest snake I’ve seen in the wild around here!

What’s your favorite summertime fruit?  Or fruit/veg/fungus you scout for and harvest from the wild?

PS – A wild black raspberry fact sheet

Welcome back to our Mycotoxin Series!

Patulin wouldn’t be the first mycotoxin I’d typically introduce, but it has been in the news recently.  Patulin is produced by species of Penicillium, Aspergillus and Byssochlamys, which are filamentous fungi or “molds”.  Patulin can be found contaminating products like fruit, grains and cheese; however, apple juice is of most concern.  And let’s be real, it’s the bruised, damaged and misshapen apples that go into juice (blemish-free are reserved for fresh market’s picky consumers).  However, apples with rot (see below) should NOT go into juice or cider production due to patulin concerns.

apple with Penicillium expansum

Apple infested with Penicillium expansum, a patulin producer.
[NOTE: The blue-gray growth is the fungus. Patulin (waaaaay too small to be seen by the human eye!) is produced by the fungus and spreads into the rotten apple.]

Photo: Puel et al. 2010. Toxins (Basel). 2(4): 613–631.

In April 2013, Winn Dixie brand apple juice was voluntarily recalled due to patulin levels over 50 parts per billion (ppb).  In June 2013, researchers from the University of Granada reported that more than 50% of commercial apple juices tested contained >50 ppb patulin (50 ppb is the “limit” for patulin in both the US and EU).

Healthy apples

Healthy apples

Patulin in apple juice is of particular concern as this product is frequently served to young children.  In fact, some of the commercial juices tested in the aforementioned study were specifically produced and marketed to children. This toxin is a suspected carcinogen and symptoms of a patulin mycotoxicosis (poisoning) are gastro-intestinal inflammation and ulcers, weight loss, swelling, convulsions and impaired immune response (source).

While I’m not a medical doctor or veterinarian, eliminating the contaminated product from one’s diet often alleviates the symptoms.  However, acute mycotoxin poisonings are rare in the US (especially for humans).  Chronic exposure to low levels of mycotoxins is much more concerning and is difficult to study.  Hopefully, juice producers will step up their mycotoxin testing protocols to reduce the levels of patulin on the grocery shelves.

Optional subtitles: Why should I care? Do I really want to know? Thanks a lot Debbie Downer.

Consumers are becoming increasingly aware of and passionate about food quality and safety.  Not a day goes by that you don’t hear buzz words like “organic”, “GMO”, “hormone-free”, “free range”, etc.  Here in the United States, we have a (relatively) safe and secure supply of food.  However, when that security is compromised, it can be big news:

GMO wheat found in Oregon (2013)

Salmonella (2012) and Listeria (2011) found on cantaloupe

E. coli on salad greens in California (2006)

Over the next few weeks I’d like to talk about another threat that can also sicken humans and animals but doesn’t often receive a lot of press: Mycotoxins.  Mycotoxins are pervasive and fascinating, in my opinion.  However, I did spend much of PhD and post doc studying them…

What is a mycotoxin? “Myco” means fungus and a toxin is a poison; mycotoxins are small compounds produced by some fungi that are harmful to humans and animals in small doses. Symptoms of mycotoxin poisoning in humans and animals are known as mycotoxicoses. Mycotoxins associated with “poisonous mushrooms” are easy enough to avoid (don’t eat them!).  However, mycotoxins are frequently found contaminating food and feed products and are consumed unknowingly.


Many species of fungi that produce mycotoxins are also plant pathogens.  As part of their infection and colonization of the plant, they produce these toxins which end up in parts of the plant humans and animals eat. I’ll be profiling specific mycotoxins in the weeks ahead, but (spoiler alert!) some of the crops frequently contaminated with mycotoxins are wheat, corn and peanuts.

Interestingly, we don’t know why fungi produce these toxins.  Hypotheses include antiherbivory (protect a host plant and fungus from being eaten), defense against competitors (a weapon against other fungi or microbes), promotes virulence/aids in causing disease or performs some unknown function in fungal cells.

Stay tuned for more in the Mycotoxin Series.

PS – Fungi are really cool organisms and produce many compounds that have been beneficial for humans, such as dyes, penicillin, statins (for high cholesterol), etc!

The stories I’ve been reading…

But first a gratuitous wheat shot, because I can’t resist those amber waves of grain:


1. It was reported last week that Monsanto’s Roundup-ready (glyphosate-resistant) wheat was uncovered in Oregon.  The catch?  Monsanto field-tested the wheat nearly 10 years ago but never released it for commercial use.  Roundup-ready corn and soybeans, which are resistant to the herbicide glyphosate, are widely grown in the US. However, these crops are generally processed or used as animal feed, whereas wheat is consumed directly by humans. There is global alarm over genetically modified (GM) foods in our diets and prolonged exposure to these foreign genes. Monsanto dropped the GM wheat project over producers’ trade concerns. As a result of this finding in Oregon, Japan has suspended wheat imports from the Pacific Northwest. Japan is the top importer of US wheat. So far there is no evidence that GM wheat has entered the food supply, but one has wonder if the presence of GM wheat on one Oregon farm is a unique occurrence.

Update: Monsanto is being sued by farmers in the Pacific Northwest over loss of business due to the GM wheat scare.

2. Scientific American reports another contributing factor of honeybee colony collapse may be the alterations to domesticated honeybee diets.  Of course the natural food source of the honeybee is its honey, but when we harvest it for human use the bees are given sugary syrups instead.  Most researchers agree that pesticide use is the predominate cause of colony collapse, but poor nutrition certainly adds to the bees’ stress, I would think.

What have you been reading?