Turkey cannot be the only culprit of induced drowsiness after
a Thanksgiving meal.

Tryptophan is an essential amino acid. An essential amino acid is one that our bodies cannot synthesize, so it must come from food or supplements. Tryptophan is not only a building block in protein biosynthesis in our body but also a biochemical precursor for synthesizing Serotonin, Melatonin and Niacin. Both Serotonin and Melatonin are factors in inducing drowsiness and sleep. Serotonin is a neurotransmitter that facilitates emotions including desire, body temperature, sleep, appetite and metabolism. Serotonin can also be converted into Melatonin, which further regulates sleep, maintaining the circadian rhythms of several biological functions.

The foods that contain Tryptophan are usually protein-based and include chocolate, oats, milk, yogurt, cottage cheese, red meat, poultry, fish, eggs, along with specific nuts and certain fruits. However, turkey contains the same amount of Tryptophan of other meats. Most meats contain .25 grams of Tryptophan per 100 grams of food while dried egg whites contain 1 gram of Tryptophan per 100 grams of food. Turkey cannot be the only culprit of induced drowsiness after a Thanksgiving meal. If this was indeed true, people would be drowsy after any normal meal containing meat as the levels of Tryptophan are equivalent.

The other two denominators with the Thanksgiving meal are high carbohydrates and fat. An average Thanksgiving meal can have 3000 calories and 239 grams of fat. In comparison, United Nations FAO says the average American consumed 3770 calories per day in 2001-2003. It has been shown in studies in both animals and humans that a meal high in carbohydrates and fat triggers Insulin. Insulin them stimulates the uptake of large neutral branched-chain amino acids, known as LNAA.

Tryptophan does not fall into the LNAA family and thus the ratio of Tryptophan to LNAA in the blood stream increases when Insulin is released into the blood stream. Less competition for transporters in the blood stream results in the uptake of Tryptophan across the blood-brain barrier and the synthesis of Serotonin and Melatonin. This in turn creates the lethargy and drowsiness common after the Thanksgiving meal. Therefore it is not turkey alone that ends in a nap after Thanksgiving dinner. It is a collaborative process. Without the intake of carbohydrates dressed up as rolls, sweet potatoes, mashed potatoes, stuffing and pumpkin pie, the Tryptophan in the iconic Thanksgiving turkey would have too much competition for synthesis. Insulin clears away the competition and in turn isolates Tryptophan in the blood stream enabling it to be readily synthesized. The whole meal is responsible for the drowsiness. The next question that could be posed is this the body’s way to have us slow down to aid digestion?

DNA magnified 850,000 times through a scanning electron
microscope

This should be a chance to pull DNA out of beef, strawberries, kumquats or even yourself and learn that you have around 100 billion miles* of DNA inside of you. In case you're interested, that'll reach from the Earth to Pluto and back when Pluto is farthest from Earth. And that is one person's DNA.

Add up everyone's DNA in the world and you get 125 million light years of DNA. (At least I think you do… these numbers are getting ridiculous!) That'll get us to the galaxy Andromeda and back 25 times. Add up all the DNA on Earth and… OK, that's probably enough of that.

There isn't just a lot of the stuff but it is amazing to me how similar all human DNA is. The latest estimates are that people are around 99.5% the same at the DNA level. That means that all those light years of DNA are mostly the same old thing just copied over and over.

Notice the mostly. With 6 billion letters of code in every person, a 0.5% difference means 30 million differences between you and me. It is these differences that make me look different than you. And to a varying degree, make me act differently than you.

This code doesn't work in a vacuum either. The environment can change how it works which is a big reason identical twins aren't really identical. And one of the reasons why it is so hard to figure out the genetics of complicated diseases like diabetes or heart disease.

Our DNA also changes with time. Things in the environment might damage it. Or our own cells can make mistakes when they make copies of themselves. What this means is that today's light years of human DNA will be different than the same stretched out DNA in 100 years.

This also means that you have some cells in your body have different DNA than the rest of your cells. And if a DNA change happens in sperm or egg cells, then they are passed on to the next generation. Which is where all the wonderful diversity around us originally came from.

As you can see, there is a lot about DNA to celebrate. It is huge and mysterious and we're just starting to get a good grasp on what it is all about.

I plan to spend the morning of DNA day at The Tech Museum in San Jose exciting kids (and hopefully some adults) about DNA by running five different hands on genetics programs all at once. It'll be a blast!

I have searched high and low for a list of DNA day activities here in the bay area but I haven't come across any. Does anyone know about other DNA day celebrations here in the bay area?

* Each cell has 6 feet of DNA and we are made up of around 50-100 trillion cells.

Dr. Barry Starr is a Geneticist-in-Residence at The Tech Museum of Innovation in San Jose, CA.