Friday, March 18, 2005

Sometimes The Reporting Is More Interesting Than The News ...

... and the reporting following the sequencing of the X chromosome and a study on the inhibition of it (two articles in the latest number of Nature) is definitely one such case. Of course, the reported facts are basically correct - facts not reported, and the "filler text" in between is what I find interesting and/or amusing.

Probably very few people reporting on this have read the actual Nature article on the sequencing - it is definitely not a light read, and the figures do not help if you are not a geneticist already. Most of them - the people writing about this - probably read the Nature News entry (free) or the Nature News and Views entry (subscription), so most of the reporting covers X gene inhibition. There are also several news releases out from Reuters and such.

Let's begin with a list of links:
Nature News
Science Now
New Scientist
BBC News

Guardian Unlimited
FOX News
Washington Post
The Scientist
National Human Genome Research Institute

Most amusing so far was definitely Washington Post's Rick Weiss (probably not intentionally, or maybe he is so subtly ironic that I do not realize it) who found it important to cite David Page, interim director of the Whitehead Institute for Biomedical Research in Cambridge, Mass., who states that the X chromosome is not as "pink" as one might believe and that in fact, it can be considered rather "blue" since men also have one.

All men who have been afraid that they where tainted by "pinkness" may now take a collective deep breath in relief.

Weiss begins his article by stating that "She has been slow to reveal secrets, but the X chromosome has now bared it all". (What's with the reference to strip-tease?) Otherwise, it covers mostly the same ground as the other articles, with an interesting aside on how sex chromosomes first evolved in reptiles and gradually became X and Y.

Nature News' Erica Check focuses on the silencing of one of the two X chromosomes, a mechanism that ensures that women do not get "too much" of the expression of the genes found in X although they have double copies of it. The choice of which X to suppress is made, randomly, in the beginning of development. One of the two reports in Nature now shows that this suppression is not as effective as previous ly thought: at least 15% of the genes in the "inactive" X are expressed, in some women up to 25%. Thus, it is probable that women are more genetically varied than men, and that differences between women could be rather big due to this differential expression. (This is 200 to 300 genes we are talking about)

Genetically determined diseases on the X chromosome could thus have a different level of expression from woman to woman, but a binary expression in men. Science Now's Elizabeth Pennizi covers approximately the same issue, but in a much shorter text. New Scientist (David Bainbridge) has an excerpt of an article from their paper-version on the web that seems to mention the same things as well.

The Scientist's Stephen Pincock has written a surprisingly long article compared to how little of actual facts it contains, but is the only one so far I've seen citing Nature News and Views' (not to be confused with Nature News; subscription required) Chris Gunter (but then again, he cites rather many people in this piece).

If you want to read only one article, I recommend Nature News and Views (Chris Gunter), if you have a Nature subscription. It's detailed but accessibly written, covering both the X sequencing and X gene activation. She also mentiones something that I find especially intriguing: the amount of "escaping" genes is not static, but varies with age - more genes are expressed in the young than in the old.

If you want to read more about sequencing rather than X gene activation, Washington University has a nice news entry covering the problems, technical details and methods used in more detail.

Via Star Tribune I find something that I've been wondering but not yet bothered to calculate: the level of genetic difference between man and woman. It is 2%, according to Robert Lee Hotz, which would make it bigger than the often cited 1.6% difference between human and chimpanzee. Go figure. Duke University genetics expert Huntington Willard is cited as saying: "In essence, there is not one human genome, but two -- male and female."

And with a 200 to 300 genes possible difference between women, maybe you should not even talk about one female genome, but several. Given that many medicines are almost exclusively tested on men, this should be enough to give the medical companies gray hairs as they realise that in some cases, the right thing to do is having several test on women with differing genomes. Ouch, that would become expensive.


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