Careful What You Choose

Dr. Barry Starr Post on Jan 04, 2010 by
Topics: Health
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When choosing an embryo, a little bit of knowledge is a dangerous thing.

People often think about certain versions of a gene as either good or bad. One that leads to depression is bad while one that protects you from HIV infection is good.

For most genes this is almost certainly too simplistic a view. Many versions of genes can be good or bad depending on your situation.

For example, the delta 32 version of the CCR5 gene can make you more resistant to HIV infection. But it also makes you more susceptible to infection by the West Nile Virus.

Which version is best for you depends on where and how you live. If you’re an IV drug user who lives somewhere up north, then you would probably benefit most from the delta 32 version. But if you are a faithfully monogamous man in Africa or Central America, then you might do better with the more common version of the CCR5 gene.

As I talk about in a recent GeneWatch article, the same is true for the SERT gene and depression. This gene comes in two versions, long and short.

Studies have shown that people who only have the short version are at a higher risk for depression. A deeper look at the data shows that this is only the case if these people had a traumatic childhood. People with two short versions who had a happy childhood are actually more resistant to depression than people with the longer gene versions.

This all matters because we are at the point where you can choose some of your child’s gene versions. And too simplistic a view of genes could cause you to make the wrong choice.

People who undergo in vitro fertilization (IVF) can go through an additional procedure called preimplantation genetic diagnosis (PGD). Basically PGD allows you to look at an embryo’s DNA before it is placed in the womb. This means that when multiple embryos are created, you can choose which one to implant based on its genes.

Fortunately we can’t really change the embryo’s DNA for the foreseeable future so you’re stuck with whatever genes you and your partner can contribute. But as we are able to look at more and more genes with less and less DNA, we are getting very close to a Gattaca-like future where we can choose many of our children’s genes.

And as the two previous examples showed, this won’t be a simple choice! There are undoubtedly hundreds of genes just like these where what effect they have on someone depends on how and where that person lives, how they were raised, etc. It might be best to restrict this sort of thing except for cases where the child might end up with a devastating illness like cystic fibrosis or sickle cell anemia.

In some ways, this sort of thing is already being restricted. For example, when a fertility doctor in L.A. suggested that he might offer parents a chance to choose what eye, hair, and skin color their children might have, the public uproar shut down the service before it even began.

I’m not sure that less politically sensitive gene selection would cause such a furor. It may be that we need some sort of government regulation to protect people from what they don’t know. Or maybe parents need to take a course before selecting which embryo they want…

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  • Bo Wang

    Dear Dr. Starr,
    I have read your paper “Chromosome Fusion: Chance or Design?” . I think I found an evidence for your assume.
    We have found an ancestry of robertsonian translocation in our clinical work (figure 1). Ⅳ1 is the proband. He asked for our help because his son (who has been dead) was a sick of cerebral palsy(1,2). We testified(3) that his karyotype (figure 2) is 44,XY,der(14;15)(q10;q10),der(14;15)(q10;q10). We call this karyotype “diplorobertsonian translocation”. His wife’s karyotype is normal. We found out that his parents(Ⅲ1 and Ⅲ2) are near relatives after asking the family history. His father’s karyotype is 45,XY,der(14;15)(q10;q10), and his mother’s karyotype is 45,XX,der(14;15)(q10;q10). For Ⅳ1, we consider that he is a new kind of human being because of these two points: The first reason is that he looses the genetic material of 4 short arms of chromosome (2 short arms of 14th chromosome and 2 short arms of 15th chromosome) and 2 kinetochores. The second reason is that he can steadily produce sperm which contain 22 chromosomes(The test show that the amount and energy of his sperm is normal). If he marry to a women whose karyotype is 44,XX,der(14;15)(q10;q10),der(14;15)(q10;q10), they can produce the offspring that all have 44 chromosomes.
    Because Ⅳ1 looses the genetic material of 4 chromosome galianconisms and 2 kinetochores, and the two derivative chromosomes of him root in one ancestor, the gene of these two derivative chromosomes have the high homozygosity, he is a perfect gene knock-out model for the research of the gene in galianconisms and kinetochores of 14th, 15th chromosome.
    It is well known that human being came from anthropoid. The number of anthropoid’s chromosome is 48, if we splice 2nd and 12th chromosome of anthropoid together, it is similar to 2nd chromosome of human being. With a view to this ancestry, we adventurous assume that chromosome translocation (especially robertsonian translocation) provide the material for evolvement.

    Figure 1: the ancestry of robertsonian translocation

    Thanks again. wait your e-mail!

  • Bo Wang

    Dear Dr. Starr,
    I am sorry for my poor Enalish! my email is [removed by editor] , wait your e-mail!

  • http://www.thetech.org/genetics/index.php Barry Starr

    Wow that is very cool and probably more appropriately commented on at our other blog. Basically you have an example of a human with 22 chromosomes that could successfully have children with another human with the same 22 chromosomes. For example, if he had a sister with a similar chromosome pattern, their kids would found a group of humans that could not interbreed with the other humans. I'll definitely email you to see the results! Maybe I could even blog about it.

  • Bo Wang

    he is about 25 years old. he has a sister.

  • http://www.eesti.ee Gunnar

    Can the guy with 22 chromosomes have children with a 23 chromosome woman? If so the guy with 22 chromosomes(lets call him guy22) has lots of children then some of them will have the 22 and some 23 chromosomes. Lets say after a long while there is a small population(or big) of 22 chromosome people. If at any time from the beginning of the guy22, any two 22 chromosome people mate then we get someone who wont be able to mate with people23(23 chromosomes) but will be able to mate with another 22?
    Why is that guy so special? As I understood the fused chromosome wont on its own stop anybody from reproducing? I read form some other forum that there are some butterflies that have big chromosomal difference in the same spices and still mate and have fertile offspring. Im sorry if my question is hard to understand- I have poor explaining skills:P
    Just to repeat- guy 22 can have children with woman23? guy22 and sister 22 have a child22 and he/she wont be able to mate with person 23? Why?
    Thank you for your time.

  • http://www.thetech.org/genetics/ Barry Starr

    The guy with the 22 chromosome pairs could have kids with a woman who has 23. These children might then have difficulty having children as we talk about at http://www.thetech.org/genetics/ask.php?id=12 because they will now be balanced carriers just as the 22 guy's parents were. The big deal is that to my knowledge this hasn't yet been seen in people and it provides for a way for our ancestors to have gone from 24 pairs to our current 23.

  • Bo Wang

    The guy with the 22 chromosome pairs asked for chromosome examination due to his wife produced a cerebral palsy child, but the child had been died at that time. we presume the karyotype of the child is 45, XY, der (14; 15) (q10; q10), and we do not know why his wife produced a cerebral palsy child.
    I want to report this family on a research journal.

  • Bo Wang

    I can not Leave a reply on your that blog"Chromosome Fusion: Chance or Design?"