Why does the hair color of children often change color as they grow older? My brother, sister and I all had light blond hair as young children which gradually darkened to brunette by the time we were teenagers. Both parents are brunette. My husba

-A curious adult from Kansas

October 26, 2004

This is a great question that gets at the root of what our DNA does. People's hair and eye color can change over time, they can become less tolerant of milk as they get older, etc. What is going on?

The quick answer is that for people to get the traits encoded in their genes, the genes need to be turned on. You can think of a gene as a recipe. A recipe in a cookbook does you no good until you open the book, get the ingredients and follow the instructions.

Hi. Well my grandmother on my father\'s side has amelogenesis imperfecta (that is where there is no enamel on the tooth). My father got it as well as his 2 sisters and one of his brothers. For one of his sisters, 2 out of 4 children got it; a girl

-A high school student from Trinidad and Tobago

I love these sorts of gene sleuthing questions! There are two types of amelogenesis imperfecta (AI). In one type, boys and girls have an equal chance of getting the dominant gene for AI. In the other, girls are more likely to get the dominant gene. Since both types are dominant, the only way for your kids to get it is if you or your future spouse has the disease.

Is it possible to create a picture, like a photo, of a person by using that person\'s DNA? Is there any research being done in this area?

-A curious adult from California

October 19, 2004

What a cool question! I never thought of something like this even though I probably should have. I would love to see what Genghis Khan or a Neanderthal really looked like.

I am a redhead and I have Rh negative blood. Is there any genetic correlation between the two? Also, what is the difference between Rh negative and Rh positive blood types? Thanks

-A curious adult from Maryland

October 15, 2004

Lots of traits seem to come together...like blonde hair and blue eyes or red hair and freckles. In this case however, your red hair and your Rh-negative status are just a coincidence, not a case of genetic correlation.

So why do blonde hair and blue eyes but not red hair and Rh factor usually come together? Blonde hair and blue eyes are often found together in people because the genes for each trait are close together on the same chromosome.

No one knows what the Rh factor does, but we do know that it doesn't have any effect on your health. For almost all purposes, Rh-negative and -positive people are no different from each other. The only time the Rh factor status of a person is important is when a woman is pregnant.

If a mother is Rh negative and she is having a baby that got the Rh gene from the father, then there could be problems for the baby. But why?

Can yellow, obese Agouti mice have brown pups or are they all yellow?

-An undergraduate from Utah

April 7, 2011

Yes fat, yellow mice can have thin brown pups. Even if their genes make it look impossible.

How can the pups be brown when their genes tell them to be yellow? By the environment marking the genes involved and changing how they work.

Before getting into this, let's first talk about the genes involved in how pups end up yellow or brown. Then we can delve deeper into how the environment can change how a gene works.

Yellow is Dominant

Agouti is one of the key genes involved in making a mouse brown or yellow. Small differences in the versions of the agouti gene cause differences in colors or hair patterns. So one version, the dominant agouti gene (A), directs cells to make the yellow pigment and the recessive version (a), tells them to make a brown pigment instead.

For example, scientists have found that changing the diet and toxins that pregnant mice are exposed to can change the expression of the agouti gene in their pups. So in addition to the genes the moms hand down to their offspring, they also pass an 'epigenome' along. And the epigenome depends on what the moms are exposed to in their environment.

When scientists fed pregnant yellow mice diets rich in nutrients containing methyl-groups, like folic acid and vitamin B12, the agouti gene in pups got switched off. And the pups from such mice were brown and thin, not fat and yellow.

My boyfriend has 3 sisters whereas I have 2 sisters and no brothers. What are the chances of him and I having a baby boy?

-A high school student from Trinidad and Tobago

October 12, 2004

This is a really great question that we get a lot in one form or another. The quick answer is that your chances of having a boy are most likely the same as everyone else's.

This is because the odds of something happening apply to each time it happens -- it doesn't matter what came before. Let's use flipping a coin as an example.

How is it that DNA can be extracted and read from long past fossils? Doesn't the drying and age affect the DNA? If we can clone a sheep from its DNA, why not a dinosaur?

-A curious adult from California

October 5, 2004

What fun questions. DNA is actually pretty stable for a biological molecule, particularly under conditions that are dry, cold and airless. DNA won't last forever, but it can last a long, long time.

However, it won't survive intact. What happens is that the ridiculously long strands of DNA break into smaller and smaller pieces over time. After an even longer time, the pieces begin to break more and more until eventually there is very little left.

My 27 year old son died in March 2004. He was quadriplegic due to an assault 6 years ago. The hospital said he had a septic infection. He was awake and talking and then they were putting on a respirator and his heart stopped. They got it going t

-A curious adult from Minnesota

I am so sorry about the loss of your son. Most likely the DNA from your son won't be able to tell you why your son died; at least not now with our current knowledge.

Since I'm not a medical doctor I won't comment specifically on the cause of your son's death. However, the fact that he had a bacterial infection when he was admitted to the hospital is suggestive. Testing your son's DNA will not provide much information about the infection itself. But it might help us understand why it hit him so hard.