Sunday, November 20, 2005

Making babies   posted by the @ 11/20/2005 11:18:00 AM

Two stories have been ironically juxtaposed in time on the front page of the NY Times web site:
Hello, I'm Your Sister. Our Father Is Donor 150.
The Problem With an Almost-Perfect Genetic World

Most likely these stories got there because of the pictures of cute little kids. However, the coincidence makes for an opportunity to point out a bit of cognitive dissonance about the topic of genetics and reproduction.

First, let me point out that there's a lot of interesting discussion in these article and you should read them for that sake. I love that the half-siblings from sperm donors feel a kinship relationship despite the fact that many are first meeting in their teens (note half siblings are as related as [correction: Uncle/Aunt - Nephew/Niece pairs]).

However, some aspects of the sperm donor topic go unexplored. With a seemingly unlimited supply of sperm in the world, why are so many children being born from the same donor? The answer is, quite obviously, that some donors are more attractive to mothers than others. Since the only thing these donors are giving to their children are half a complement of chromosomes, the attractiveness is obviously in the genes.

Now consider the repro-genetics article. This article is better than most in that it doesn't consider the ridiculous (but often asserted) position that wanting to not give birth to children with disabilities literally implies that we want to destroy existing children with those disabilities or that we regret their existence in such as way as to value them less as persons. They consider more reasonable concerns, such as the fear that reduced incidence of children born with genetic disorders will reduce funding for treatments (a harm to the children already born). However, I would argue that none of this is an argument against screening -- we would not chose to give children these disabilities to increase funding -- but it is a legitimate issue to consider.

However, consider this segment:
"Where do you draw the line?" said Mark A. Rothstein, director of the Bioethics Institute at the University of Louisville School of Medicine. "On the one hand we have to view this as a positive in terms of preventing disability and illness. But at what point are we engaging in eugenics and not accepting the normal diversity within a population?"

Rothstein seems to be suggesting that extreme deviation from the population mean is an acceptable target for screening, but that (for example) variation within 3 SD of the mean should be off limits. I fail to see any good argument for such a differentiation.

Now let's tie these stories together. As I noted about repeated use of the same sperm donor, there is apparently a selection going on at the level of maternal choice of a sperm donor among men who are within the normal range of variation that Rothstein had in mind. This doesn't seem to be eliciting concern and neither should screening for abortion in that range.

It appears that "poor man's gene therapy", as Rothstein calls selective abortion, is already happening prior to conception and increasingly through prenatal screening. Looking forward: "Soon, though, pregnant women may be offered a gene-chip technology that can perform hundreds of tests at once for a few hundred dollars." Maybe not a microarray platform, but medium through-put genetic screening is already feasible using commercial technology.