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.

Red hair genes will be diluted but will not go away.

The guy from the bookstore must have read one of the stories about the imminent demise of redheads that flashes across the media landscape every few months. People with red hair have to deal with headlines like:

"Redheads Set for Extinction."
'Will rare redheads be extinct by 2100?'
"Gingers Extinct in 100 Years."

The reporter suspected these stories weren't right and wanted to write a story about it. She called me to get some science to back her up. I was able to reassure her that redheads weren't going the way of the dodo. They'll become much less common, but there will probably always be red haired people around.

To understand why redheads will fade but not disappear, we need to dig a bit deeper into how red hair works. Red hair happens when both copies of the MC1R gene do not work properly. (Remember we have two copies of almost all of our genes–one from mom and one from dad.)

So if you're a redhead, you inherited a nonworking copy of MC1R from both your mom and your dad. If you get a non-working copy from only one of them, then you won't have red hair. You'll be a carrier.

Right now redheads are at an artificially high level in the human population because their recessive red hair genes are concentrated in North America, Europe, and Australia. For example, 10% of Ireland and 2-6% of the U.S. has red hair.

These numbers are maintained because carriers and redheads keep making new redheads with each other. But as barriers go down, their red hair genes will flow out of these populations and into the human gene pool.

Red hair genes will become diluted in this pool but they won't be completely swamped out. Even as redheads decline in numbers, their genes will remain constant. It will just be less likely that two carriers and/or redheads will meet and have babies with red hair.

This is all interesting but it got me to wondering about how many redheads there will be in the distant future when all the mixing is said and done. We can use something called the Hardy Weinberg equation to figure this out.

This equation works great for simple dominant/recessive traits like red hair if we know how many of each gene version there is. To do this, we need to figure out how many redheads and how many carriers there are in the world.

It is easy to figure out how many redheads there are–you can tell who they are just by looking at them. But figuring out carriers is a lot harder. We can make guesses based on the number of redheads (again using Hardy Weinberg) but until we sequence a lot more MC1R genes, they'll only be guesses.

The numbers I have seen floating around are that around 1% of the world's population has red hair and that around 4% carry the red hair version of MC1R. This means that there are around 65 million or so redheads in the world and 260 million carriers. (This sounds high to me but these are the numbers out there.)

When we use these numbers and apply the Hardy Weinberg equation, we end up with a final percentage of redheads of 0.1% or 6.5 million. This is quite a fall from current levels but they are hardly wiped out!

There are lots of assumptions* in these calculations that might cause the number of redheads to actually be more or less than 0.1%. But unless there is some red hair specific catastrophe or people start burning them as witches again, redheads are here to stay.

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

*Some assumptions used:

1) There are no barriers to finding partners
2) The 4% carrier number is an accurate one
3) Two non-workingMC1R genes produce red hair in all genetic backgrounds
4) Other assumptions described here

Lake Toba is all that is left of the volcano
that nearly wiped out mankind.Last blog I talked about how East Africans are genetically more diverse than Asians. Who are genetically more diverse than Native Americans.

From all of this you might have concluded that people are pretty different from each other. They aren't.

People are surprisingly similar at a genetic level. For example, any two people from anywhere on Earth are more similar than two chimps from the same troop. Why are we all so alike?

One possible explanation is that something in our collective past nearly wiped us all out. And we all come from the few survivors who were left.

A likely candidate for this near annihilation event is the Toba volcanic eruption that happened in Indonesia 75,000 or so years ago. This eruption was huge.

It was equivalent to around 1 billion tons of dynamite and was about 3000 times more powerful than the Mount Saint Helens eruption in 1980. It also may have reduced the average global temperature by 5 degrees Celsius, darkened the world for 5 or 6 years, and plunged the world into a new Ice Age.

As you might imagine, this eruption had dramatic effects on species around the world including our own. Estimates of how many people were left range from around 1000-10,000 breeding pairs. The theory is that we are all so alike because we share these survivors' DNA.

Whether true or not, a bottleneck in our past would not make us unique. Lots of species go through these near death experiences.

Scientists think cheetahs went through one around 10,000 years ago. Cheetahs are all so similar genetically that veterinarians can do skin grafts with "unrelated" cheetahs.

And of course, people have created bottlenecks in species too. For example, in the late 1890's there may have only been 20-100 elephant seals left in the world because of hunting. Now there are at least 150,000 spread across the west coast.

Species are in danger long after they go through a bottleneck. They have a pretty limited gene pool which means they may not be particularly healthy and are in danger of being wiped out by, for example, a single disease. Humans are probably OK in this regard (consider natural resistance to HIV for example) but elephant seals, bison, and cheetahs, and many other species may not be.

Fortunately for us we successfully came through our bottleneck. Hopefully, the animals that we've nearly wiped out will too.

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

I remember loving science class as a kid. The paper-maché messes, the bubbling baking soda, all of the wonderful experiments… I loved it all. Now, many grammar school kids are lucky to get 15 minutes of science education a week. Hardly enough time to get them imagining future careers as scientists, engineers and inventors.

Between the lack of time given to science education, and the structure imposed by curriculum standards, museums need to be part of the education equation. My boss has a saying: "Give random a chance." I love this quote because it speaks to the role informal educational resources like science museums need to be playing. By exposing young people to the experiences and programs in a museum, who knows what might really resonate and inspire?

For over 20 years, The Tech's Tech Challenge program has presented kids with an open-ended problem for which there is no one right answer. It forces participants to use their knowledge and ingenuity to solve the problem. For example, this year the Challenge (called Water Works) is all about moving water from a stream up to a village without electricity. There is no one right answer, and there are lots of ways to solve this problem.

Participants are 5^th to 12^th graders who will work in teams of 2-6 to explore solutions to solving this real world problem. Along the way, they will hit some roadblocks and come up with some duds. And that's OK because it is here that kids will learn that failure is an important part of problem solving. We have a great quote etched into a wall on the outside of The Tech from Intel co-founder and philanthropist Gordon Moore that says, "If everything you try works, you are not trying hard enough." Through failure, many of the Tech Challenge teams will come up with a far superior solution.

This year we're going international for the first time by partnering with the City of San Jose's Sister City program. On the final event day, where all of the teams come together to present and demonstrate their solutions, we'll be webcasting in teams from far-away locations, and look forward to seeing and hearing how kids from other countries have tackled the challenge. Hopefully the involvement of other cultures will drive home how important it is to be inclusive to come up with better ways to solve problems.

I just looked at the U.S. Census Bureau web site for the latest world population number, and today there are 6,650,846,379 people on Planet Earth. One in five people on Earth don't have access to safe, clean drinking water, which means that 1.3 billion people are suffering from lack of water. As this year's Tech Challenge participants work on solutions to a global water problem, I hope they get excited (or more excited) about science and remain engaged, even they don't get to study it much in the classroom.

Lisa Croel is the Marketing Director at The Tech Museum of Innovation in San Jose, Calif.