I am on my 14th week of pregnancy. I have to decide whether to have an amniocentesis done. I'm 35 years old and consider myself very healthy, no genetic problems in my family. In my husband's family there have been some cases of cancer. His dad

-A curious adult from Canada

For women 35 years and older, an amniocentesis is usually done to test for new genetic problems. As a woman gets older, she is more likely to give birth to a baby with genetic diseases like Down syndrome.

There are certain diseases that run in a family that can be tested for with an amniocentesis. These are usually simple, single gene diseases like cystic fibrosis or sickle cell anemia. The cancers you describe are neither simple nor caused by a single gene.

My husband and I are first cousins and I am worried about our future kids. Are our kids at a very high risk of coming out retarded or something? People are always drawing that annoying conclusion and I try not to let it bother me...I\'ve done some

-An undergraduate student from New York

I can see why you might be concerned about your kids. We've all heard about what supposedly happens if cousins marry. A recent study, though, showed that while there is increased risk of some genetic disease, the risk is actually smaller than a lot of people might think.

I have a question about my son\'s health and segmental NF. During a routine annual physical exam, at the age of 8 yrs. old, I questioned my son\'s pediatrician about the noticeable freckles in my son\'s armpits and on the left side of his neck (whi

-A curious adult from Indiana

I can understand your concern...a genetic disease diagnosis can be a scary thing, especially for your kids. If your son does have segmental NF (more about that later), it would be useful for him to know this for when he wants to have children. Fortunately, segmental NF is usually not dangerous in itself. But, there is a chance that your son could pass the more serious, full NF, down to his kids.

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.