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What food is sweet and good to eat?

Dear Dr. Universe: What food is sweet and good to eat? – Sophia, Pullman, WA

Dear Sophia,

There are quite a few foods that are sweet and good to eat. A lot of them are fruit, said my friend Pablo Monsivais. He’s an associate professor at the Washington State University Elson S. Floyd College of Medicine. » More …

Why do feet smell?

Why do feet smell?

-Jose, 10, Costa Mesa, Calif.

Dear Jose,

We live in a world filled with all kinds of smells. Take off a pair of tennis shoes after a long day and you might even get a whiff of something pretty stinky. You can blame it on your bacteria. Millions of these tiny things live on your feet. » More …

Why are there different blood types?

Dr. Universe: Why are there different blood types?

-Sarah, Tacoma, Wash.  

Dear Sarah,

At this very moment, several quarts of blood are circulating through your body at nearly 4 mph. But as you’ve pointed out, not everyone’s blood is the same.

Your question made me wonder exactly what we mean when we talk about blood types. I decided to ask my friend Amber Fyfe-Johnson, a researcher at Washington State University who studies cardiovascular diseases–diseases of the blood vessels– in kids.

Believe it or not, she said, there are more than 20 different blood groups. We’ll stick to the main one for now: ABO. There are 4 different types in this group: A, B, O, and AB.

You have trillions of blood cells. Each blood type refers to a specific marker on a red blood cell. It’s kind of like a little flag.

In the early 1900s, an Austrian doctor named Karl Landsteiner discovered three of the little flags. Today, we call these three flags A, B, and O.

These little markers make blood types compatible with each other. If a person with Type A blood is given Type B blood, his or her body sees the Type B surface flag as foreign and rejects it.

Meanwhile, Type O doesn’t have those surface markers. There is nothing on the surface of the red blood cell to reject. Type O blood can be transferred to pretty much anyone who needs it.

Fyfe-Johnson explained that the blood types we have today evolved a very long time ago. Type A is the most ancient blood type and has been found in hominids – or pre-humans. Scientists can use DNA from some blood cells found in fossils to help figure this out. Type O probably originated next, about 5 million years ago. Scientists are still trying to pinpoint when exactly each blood type evolved.

As is often the case, there are a few ways to think about the answer to your question.

One way to think about it is that our parents pass genetic information about our blood types down to us. It’s part of our DNA. Sometimes there’s a change, or mutation, in DNA.

“These different blood types evolved as a result of genetic mutations, but what caused certain blood types to be more successful is likely exposure to infectious diseases or other environmental pressures,” Fyfe-Johnson said.

The kinds of blood types that survive infections are often the ones that outlive the others.

For example, cells that are infected with a disease called malaria don’t stick to Type O or Type B red blood cells. Those with Type A blood who are infected with malaria are more likely to have clumps of cells form that can be harmful. Especially when they form in places like the brain or heart.

People with Type A blood are more likely to have serious complications or die as a result of malaria, whereas people with other blood types could survive. This happens with many kinds of diseases, she said.

“The short story is that blood types probably evolved as a way to fight infectious diseases or other environmental pressures,” she said. “Blood types that survived were more likely to be successful.”

In a way, it’s all about survival of the fittest blood.

Sincerely,
Dr. Universe

What do astronauts eat in space?

What do astronauts eat in space?

–Rhemi, 12, St. Louis, Mo.

Dear Rhemi,

Astronauts eat all kinds of different foods up in space. The food is often similar to what we have here on Earth. But in space, there’s very little gravity. There’s very limited refrigeration, too. On the International Space Station, the refrigerator is only about half the size of a microwave. That means scientists who prepare and package astronaut food have to do it in ways that take up very little room and don’t need to be kept cold. » More …

Why does meat brown on the grill?

Why does meat get brown on the grill?

– Christina, Seattle, Wash.

Dear Christina,

You know summer is just around the corner when the smell of barbecue is in the air. It’s a great question you ask and it leads us to the Meats Lab at Washington State University. That’s where I met up with my friend and animal scientist, Jan Busboom. » More …