Whose blood do we carry, our moms or dads? Or it doesn\'t matter because it could be from either one?

-A curious adult from Massachusetts

November 18, 2004

Well, your blood is definitely all your own. But because of how the genetics of blood type works, it could seem like you have your mom's blood type, your dad's blood type, or a mix of the two.

For every gene, you get two copies -- one from your mom and one from your dad. Even though the two copies are for the same gene, you can get different versions from each parent. These different versions are called alleles.

Hi! I am doing a science fair project on DNA. I found an article stating that 20 babies were born genetically altered (BBC news). I showed my teacher the article and she has doubts whether the article is actually true. So my question is, is there

-A middle school student from California

November 17, 2004

The answer is that yes, up to 30 genetically altered babies have been born in the U.S. The genetic change is very crude and is actually the result of a fertility treatment.

Some women are infertile because there is something wrong with their eggs. The idea behind this treatment is to put the mother and father's DNA into a new egg.

I realize that humans have 46 chromosomes and chimps 48, but do we (<i>homo sapiens</i>) have more genes or fewer genes than the chimp? And while were on the subject, is the Y chromosome in humans smaller in size than the Y chromosome in chimps, me

-An undergraduate from Wisconsin

November 16, 2004

At the gene level, chimps and people are over 98% the same. Chimps and humans have a different number of chromosomes, but because they are so similar they probably have about the same number of genes. In fact, a close look at chimp and human chromosomes (see below) shows that one of the human chromosomes is really made up of 2 of the chimp chromosomes (or vice versa).

How is it that red hair shows up in people of African descent?

-A curious adult from California A redhead of African descent is about as common as a Caucasian with red eyes. And there's a good reason for this -- being an albino causes them both. Except when people are of mixed ancestry, red hair in Africans is usually caused by a kind of albinism. When people think of albinos, they tend to think of white hair, pale skin and red eyes. While this is true for Caucasians, albinism works differently in people of African descent.

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. So why if the gene is dominant does that mean you have to have the disease to pass it on? To answer this question, we need to go a bit into some basic genetics.