Well, let's get this thing off the ground. Right off the bat, Awesome Mom asked in incredibly good question: "Why does my husband think that putting ketchup on tacos is a normal thing to do?"
Given the fact that I happen to have spent some time doing basic taco research, and that I have eaten both tacos and ketchup (although not simultaneously, I must admit), I am the perfect person to answer this question (although a guy in a taco suit may also be a good candidate).
Most men do not put ketchup on tacos. It is actually a condition that occurs in 1 in 5,000 people, with a preponderance of these being men. The taco/ketchup combination is what is known as a x-linked recessive genetic disorder.
Genetically, the difference between men and women is that women have two "X" chromosomes, while men have one "X" and one "Y" chromosome. The x-chromosome does not, in fact, look like an "X" at all, but instead looks like a worm with a waistline (as pictured above). Why is it named "X" then? Well, it has a tendency to get tangled up with the other x-chromosome and so when researchers first saw it, it looked like a "X." Besides, "worm with a waistline" chromosome would just not have sounded very good.
The y-chromosome is much smaller than the x-chromosome, and does not look like a "Y" ether, but instead looks like a much shorter worm with a much lower waistline.
You may have noticed that these chromosomes are striped. Those stripes are things called genes. Genes have a tendency of alternating between black and white, which has made it much easier for scientists to crack the genetic code. Another thing that made it easier to crack the code were the little lines with numbers and letters. Nobody knew what these numbers and letters meant for many years, but through painstaking research, they have determined that these letters are a code that tells your body how to be either a man or a woman.
You may have also noted that x-chromosomes have many more genes than y-chromosomes. Many scientists believe that the feeling by many women that jeans make them look fat comes from the fact that there are more genes in a women's body, and this is actually a cry for help from the chromosomal level. Other scientists think these scientists are just full of hooey.
We get one set of chromosomes from our mother, including one x-chromosome, and one from our father: either an x or a y. For a trait to be expressed on the outside of a person, it must (in most cases) be present in both sets of chromosomes. X-linked conditions occur when a genetic trait is expressed on the the x-chromosome. The y-chromosome is too wimpy to put up much of a fuss, so a man with a trait on the x-chromosome will have the genetic trait. For a women to express the trait, both x-chromosomes have to carry the gene for that trait.
A good example of this is the most common form of color blindness. If a man has this trait on the x-chromosome, he will be color blind. For a woman to have the same type of color blindness, she must have the gene on both of her x-chromosomes. That means, a man will get his color blindness from the x-chromosome of his mother (since he had to get the y from his dad). This can be seen in the diagram below.
So it should be becoming obvious that putting ketchup on the taco is a x-linked disorder. It is, in fact, carried on the Xp-11,12 gene. This means, Awesome Mom, your mother-in-law is responsible for passing this gene on to your husband. Some have postulated that this too is a bunch of hooey and that the whole x-linked theory was made by some angry woman scientists who wanted to blame things on their mother-in-laws.
What can be done about his taco/ketchup tendency? Gene therapy is something that could help. To do so, you can either take a virus that goes for the x-chromosome and alters the Xp-11,12 gene to no longer favor this combination, or the virus can tell the y-chromosome to stop being such a wimp and stand up to that nagging x-chromosome. Since scientists are not sure what trouble an embarrassed y-chromosome would cause, this latter solution is not favored.
Putting down the toilet seat, by the way, is a trait carried on the x-chromosome as well, but the y-chromosome is sick of being pushed around in most men and makes a stand when it comes to putting the toilet seat down. Sorry, there is little hope for that one.
So that is the first installation of "Ask Dr. Rob." Hopefully it will not be the last. If you have other questions that need answering, please send an e-mail to firstname.lastname@example.org.
Thanks Awesome Mom!