At Least I Know He’s From a Good Family Remember me? It’s my turn today.

At Least I Know He’s From a Good Family Susan makes an appointment with the genetics staff. Anyways, we’re really serious about each other, and I want to make sure that our kids would be ok…you know with all the problems we have. This guy, he’s Vietnamese. His mother is Vietnamese anyway. And I’ve heard about thalassemia. Isn’t that the one that Southeast Asians can get? I’m developing a relationship with a special guy but I’m concerned about birth defects. It’s more common to that area of the world. Ok, so let’s review thalassemia.

B-Thalassemia Gene disorder: Autosomal recessive Red blood cell deficiency Common ethnicities: African decent Mediterranean decent SE Asian decent Early heart & spleen disease Treatments: Blood transfusions

At Least I Know He’s From a Good Family Well, as long as you’re not related to this guy, I don’t think thalassemia should be a problem. His father and my father are brothers. Dan is my first cousin. Oh boy…that’s the other thing I wanted to talk to you about… No. My ancestors are from England. They came over on the Mayflower I think. Are your parents Southeast Asian, Italian, or from the Mediterranean?

The geneticist explains that while Dan has about a 6% chance of carrying the gene for thalassemia, the fact that Susan is his first cousin doesn’t increase their chance of having a child with thalassemia as much as it would if Susan’s family was of Mediterranean decent because the likelihood that Susan carries the thalassemia gene is about 1 in 100, no higher than it is for anyone who is not Mediterranean or Southeast Asian. Everyone carries a handful of recessive genes that could be harmful if they pair up in the offspring. If you’re unrelated, the odds for these genes pairing up are small. The vast majority of children born to first cousins are healthy. There is a higher rate of pregnancy loss and congenital malformation. But the odds are in your favor. I’ve heard that children born to first cousins are almost always mentally retarded, still born, or have some serious defect. This makes me hesitant to allow the relationship to grow. But since you and Dan are closely related, the likelihood that you and Dan are both carries is greater.

Susan and Dan are offered carrier testing just to be safe Susan and Dan are offered carrier testing just to be safe. The geneticist calculates that even if Dan does carry a gene for thalassemia, the likelihood that they could have a child with this condition is about 1 in 400. Odds 2 carriers produce an affected child 1/4 Odds Susan Is a Carrier 1/100 Assuming Dan is a carrier 1

Odds 2 carriers produce an affected child 1/4 Susan carrier 1/2 Dan carrier 1/8

At Least I Know He’s From a Good Family No thank you. My niece is doing ok. Even if we carry the gene, I don’t think that it would change anything. If we ever have children, the doctors are going to be especially careful with PKU testing. I won’t worry about it now. Would you both like to be tested for PKU?

Essay Recently, a man and a woman planning to be married found out that they were biologically brother and sister. Both had been given up for adoption and had been raised by different families, never knowing of the other's existence. Do you think they should be allowed to be married?