Other Traits

I was doing a science project with my son and I told him that liking or not liking cheese is due to your DNA. I also told him that loving to read, play basketball,and draw etc were due to your DNA also. I also told him that being short or tall, having blue eyes or brown eye were, of course, due to DNA. However, my girlfriend disagreed saying that liking or not liking cheese is a preference not inherited. Who is right?

-An undergraduate student from Illinois

February 23, 2005

You're both right. Our DNA and our upbringing affect who we are and what we like to do.

It's a question of nature vs. nurture.

"Nature vs. nurture" is a catch phrase you might hear in the news sometimes. It refers to the debate about how much of who and what we are comes from our DNA (the nature part) and how much comes from how we are raised (the nurture part). It turns out that for a lot of things there is a combination of both at work.

This is true to some extent for even the more obvious genetic traits. Take height for example. This trait is strongly but not entirely genetic.

An example of how nature and nurture work together comes from the people of Japan. 100 years ago, the Japanese were much shorter than the average European. Were they genetically programmed to be shorter?

Probably not since they can now grow to be as tall as the average European. The difference between then and now has to do with the Japanese diet.

As the Japanese ate more protein, they were able to grow as tall as their genetics would allow. Clearly the environment can impact even strongly genetic traits like height.

But what about things that aren't physical? It might seem like things like enjoying reading, being good at basketball, or liking to draw are genetic too. There certainly are families where everyone is a bookworm or everyone can play basketball like a pro. But it's not just DNA for these traits that is getting passed along from parents to children in these cases.

For example, a family that is famous for their basketball abilities may share the genes for being tall. This would give them some advantage. However, the fact that they spend every weekend at the park playing three-on-three probably makes even more difference. (It would also explain why not all tall people are good at basketball!).

Food preferences are a good example of traits that have both a nature and nurture component.

You told your son that liking or not liking cheese is genetic. Well, this may be part of the answer, but it could also have to do with a person's very earliest exposures to food.

There is some evidence that what your mother eats while she is pregnant with you and when she is breastfeeding you predicts what kinds of foods you will like when you get older. So if your mom ate a lot of cheese, maybe you would grow up to really like it. And if she never ate it, maybe you would grow up to not be very interested in it.

But there is also a thing called lactose intolerance. You've probably heard of this because most people in the world are actually lactose intolerant and there are lots of products in the supermarket to help these people. People with this condition get gas and diarrhea when they eat things made from milk.

What lactose intolerance means is that you don't have a working enzyme in your stomach and intestines to properly digest a sugar called lactose that is found in dairy products. Most adults are actually like this, but it kind of depends on where their ancestors are from (most Northern Europeans can digest lactose, but almost 90% of Asian people can't).

Scientists have shown that the ability to digest lactose is actually due to a mutation. So if you don't inherit this mutation from your parents, you won't be able to digest lactose and you probably won't like cheese very much because of the upset stomach you'll get.

There is another gene that can affect food preferences. It determines whether you can taste certain bitter chemicals. People who have mutations in this gene think things like broccoli and tofu taste really yucky because of the bitter chemicals these foods contain. Because they can taste chemicals that others can't they are called "tasters". The really sensitive people are called "super tasters."

Having this gene mutation may have good and bad consequences. On the one hand there is evidence that tasters and super tasters may avoid some of the vegetables that are important in a healthy diet. That means that they might not be getting some of the cancer fighting nutrients they need.

On the other hand, there are some studies that say that super tasters taste all things really intensely. This makes them avoid really sugary and fatty foods, so they might end up healthier than the rest of us.

Some things about you are decided the moment the sperm and egg come together to create you...your eye color for example. But for a lot of things, your DNA just dictates a range of outcomes and your environment shapes which ones end up making you who you are.

By Erin Cline, Stanford University

Liking cheese: nature or nurture?

Broccoli can be bitter because of your DNA.