New Video: “Are GMOs Natural?”

A while back I posted a picture on twitter of a process called the “floral dip” which is science-speak for dipping a whole dang plant in a bath of microbes to make a GMO.

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Someone asked in the comments if there was an explanation of this process anywhere. I couldn’t find one, so I decided to make a video. Two years later, here is the finished product.

In this video, which I produced as a member of the UC Davis science communication and outreach group “Science Says“, I explain what causes those big tumors we sometimes see on tree trunks or plant roots, and how scientists have borrowed techniques from this natural phenomenon to add genes to plants for agriculture and research purposes. It is meant to be an educational video that cuts through the “are GMOs good or bad” debate and simply explains how they’re made. Please watch it and share it widely!

Activity: Breeding Vs. Genetic Engineering

Plant breeding and genetic engineering are incredibly useful tools. Like most tools, they serve distinct purposes. Plant breeding randomly combines the genes of two closely related plants. This is useful when both parents have several useful traits. Genetic engineering allows scientists to move specific genes between species. I used the following scenario to demonstrate the precision of genetic engineering as compared to plant breeding to freshmen at San Marin High School:


Two volunteers were selected to be “genetic engineers” and the remaining 15-20 students were “plant breeders”. Each student was given two solo cups, one representing maize (corn) and one representing its wild ancestor teosinte. Each cup contained six Popsicle sticks each representing a gene. The bottoms of the Popsicle sticks were colored green, yellow, or red. The colors represented useful genes, neutral genes (conserved between corn and teosinte), and undesirable genes respectively. Corn had three useful genes and three neutral genes. Teosinte had one useful gene (the disease-resistant trait), two neutral genes, and three undesirable genes.


Students were instructed to “make a cross” between these two species by selecting three Popsicle sticks from each cup. “Genetic engineers” had clear cups and could pick the genes they wanted. “Breeders” had red cups and had to randomly select their genes. The goal was to maximize the number of useful traits and avoid any undesirable traits.

Each of the genetic engineers selected four useful genes and two neutral genes. Breeders ended up with a variety of different combinations. Only one breeder successfully avoided picking any red Popsicle sticks; however, this student still ended up with less total positive/green traits than the genetic engineers.

The students asked what a breeder would do to generate the same optimized crop as the genetic engineers. The “breeder” whose new crop had no undesirable traits put his Popsicle sticks into a new cup and then “back-crossed” it with maize (again randomly selecting three popsicle sticks from each). After two rounds, he still had not managed to generate a variety with as many good traits as the genetic engineers. I then went on to explain that this scenario assumes there are only six genes in corn and that each of those genes acts independently. In fact there are over 30,000 genes and neighboring genes tend to be inherited together.

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Hands-on Activity: Breeding Vs Genetic Engineering by Jenna E Gallegos is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.
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Hands-on Activity: Central Dogma of Biology

As part of the Sacramento Powerhouse Science Center’s Science Communication Fellows Program, I worked with educators to develop a hands on teaching module to describe my graduate research at the University of California in Davis. I focused on the foundational subject of gene expression, sometimes called the “central dogma of biology”. In the central dogma, genes, which are functional units of DNA that encode traits, are copied into molecules of RNA. RNA is structurally similar to DNA and serves as a molecular message. The RNA is then used as instructions to construct the proteins that are responsible for recognizable traits in all organisms.


I found this hands-on activity to be effective in teaching basic concepts of genetics to students 10 and above as well as an enjoyable exercise for adults. The lesson had the dual function of explaining how genes encode traits and driving home the point that all of life is composed of the same basic building blocks, “the genetic code”.

Beads on pipe-cleaners were used to represent nucleotides (DNA building blocks) in a gene which was attached to a felt oval representing the nucleus (where the DNA is housed and copied) of a cell. I set the stage by describing a scenario in which some cells from my pet dog contaminated one of my samples of plant cells, and I needed to identify which gene belonged to the plant and which belonged to my dog, Fiona. There were two nuclei, each representing either the model plant Arabidopsis or Fiona the dog. The nuclei were fixed at one end of the table, while the “genetic code” needed to decode the gene was fixed at the other end of the table.

I then introduced a challenge: “Can you figure out: Which string of beeds represents Fiona the dog? Which string of beads represents the lab plants? The genes that make a plant a plant or a dog a dog are stored in a tiny cell compartment known as the nucleus, but the information needed to decode those genes to produce a trait (such as small or white) exists outside of the nucleus. Can you use the beads to make a copy of the message in the nucleus and then crack the genetic code to see if the message describes Fiona or the lab plants?”


There were three simple steps to unravelling the mystery. “Step 1: Pick a nucleus” (at which point I asked the students to guess if the nucleus they think represented the plant or the dog).

Step 2: Using a pipe cleaner, make an exact copy of the beaded message” (students followed the color code on their own piece of pipe cleaner, which they got to keep as a bracelet).

Step 3: Use the ‘genetic code’ on the other side of the table to decode the message. Each set of 3 beads represents the letter of a word used to describe the plants or the dog” (the encoded word was either ‘green’ or ‘furry’ depending on the nucleus). Conclusion: “Plants and dogs are very different, but the building blocks that make up their genes are exactly the same. Did you figure out which nucleus is which?”


After they had finished the exercise, I explained that what they’d just done is called gene expression, and it happens in cells all the time. “Genes are units of DNA. DNA is made up of four building blocks represented by the letters A, C, G, and T” -just like the four differently colored beads. DNA is locked up in the nucleus, but the machinery needed to translate its message into traits (proteins) is outside of the nucleus, so- “DNA is copied into a similar structure called RNA in a process called ‘TRANSCRIPTION’. This RNA message”-represented by their bracelets- “is also made up of four building blocks represented by the letters A, C, G, and U. The RNA message” -gets transported out of the nucleus, where it- “is decoded three letters at a time in a process called ‘TRANSLATION’. This process provides instructions for how to assemble the proteins that make up the physical traits of plants and animals.”

As an aside, I then went on to explain how we study gene expression in plants by making “changes to DNA then measur(ing) gene expression using a special gene that turns plants blue or fluorescent” and closed with a shameless plug for why plant science is so important and yet so under-appreciated.

I hope the reader finds this module useful for describing the central dogma in your own classroom/workshop settings.

Creative Commons License
Hands-on Activity: Central Dogma of Biology by Jenna E Gallegos is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.
Based on a work at