No, the human Y chromosome does not look like a "Y"

The Venter Institute picture shows a standard metaphase karyotype. Production and interpretation of this type of image is standard medical practice when working up various types of cancer, mainly leukemia and related disorders but also some other types, and also when doing workups for genetic disorders that can be detected at the karyotypic level, for example, trisomy 21. Notice how the chromosomes look "banded". Every band has a meaning as a landmark. This standard type of karyotype analysis is supplemented by several more recent advanced techniques. However, the metaphase karyotype is still very important. It takes a huge amount of training and practice to interpret this type of karyotype.

This is not what chromosomes look like inside a living cell, but it's an excellent way to visualize them for a useful level of analysis.

What has been done is the following - cells of interest were briefly cultured and induced to divide, and then arrested in metaphase by exposing them to the toxin colchicine. The bands are the result of subsequent staining.

Of course, even the chromosomes of cells poisoned during metaphase don't line themselves up that neatly. The old way of sorting out a karytopye, which I have done, was to take photomicrographs of cell nuclei, cut the chromosomes out of the pictures with scissors, and line them up by hand. Now it's done digitally, of course.

Most of the time, even rapidly dividing human cells are in interphase, and their chromosomes would look, if you will, like a tangle of spaghetti.

http://en.wikipedia.org/wiki/Karyotype#Observations_on_karyotypes

http://en.wikipedia.org/wiki/Cytogenetics#Techniques

http://classes.biology.ucsd.edu/bimm110.SP07/lectures_WEB/Cytogenetics%20Note.pdf

Furthermore, the Telegraph illustration shows that each chromosome arm is a separate DNA helix, only about 100 bases long. And they are not covalently bonded to each other. But they are surrounded and held together by some kind of transparent gel, maybe silica gel.

And here I'd just gotten over thinking that autosomes and X chromosomes were straight, while Y chromosomes were bent at the centromere.

As I mentioned elsewhere it is even worse: two of the chromatid halves of what supposedly shall represent an X-chroosome and the left upper arm of what is meant to be a Y-chromosome contain left-handed DNA.

I'm absolutely positive that the artist who generated the newspaper illustration intended it as totally symbolic, rather than realistic.

However, I agree that there is always some danger that naive readers will be misled by such images.

I agree that this is an artist's rendition, but there are tons of science artists who care about getting the science right, as well as producing wonderful images.

harold said: I'm absolutely positive that the artist who generated the newspaper illustration intended it as totally symbolic, rather than realistic.

callahanpb said:

harold said: I'm absolutely positive that the artist who generated the newspaper illustration intended it as totally symbolic, rather than realistic.

The 3D rendering and lighting effects are suggestive of something that is not purely symbolic. Looking at this, you would at least expect the geometry to be roughly correct. So while I agree that it is intended symbolically, it is not a good illustration. BTW, is there an electron micrograph that shows why it would be suggestive of a Y? This one http://www.ocf.berkeley.edu/~edy/genome/ shows a lot of Xs, and I assume it is accurate though I don't know the exact circumstances of how you would get that picture.

callahanpb said:

harold said: I'm absolutely positive that the artist who generated the newspaper illustration intended it as totally symbolic, rather than realistic.

The 3D rendering and lighting effects are suggestive of something that is not purely symbolic. Looking at this, you would at least expect the geometry to be roughly correct. So while I agree that it is intended symbolically, it is not a good illustration. BTW, is there an electron micrograph that shows why it would be suggestive of a Y? This one http://www.ocf.berkeley.edu/~edy/genome/ shows a lot of Xs, and I assume it is accurate though I don't know the exact circumstances of how you would get that picture.

harold said: Oops, I just noticed that maybe you thought the “X” chromosome was named for its shape. (Apologies if I’m misreading.)

The shape of things to come?

In biology X and Y, maybe Z are used to designate things discovered but not understood. For example google crayfish X and Y organs. I took physiology from a professor who studied them, so I know of them. They are in the eyestalk, and large numbers were needed for study. So his graduate students had excellent crayfish boils with the discarded eyeless crayfish.

Jim Thomerson said: In biology X and Y, maybe Z are used to designate things discovered but not understood.

The idea that the Y chromosome was named after its similarity in appearance to the letter "Y" is mistaken. All chromosomes normally appear as an amorphous blob under the microscope and only take on a well-defined shape during mitosis. This shape is vaguely X-shaped for all chromosomes. It is entirely coincidental that the Y chromosome, during mitosis, has two very short branches which can look merged under the microscope and appear as the descender of a Y-shape.