Structure of Chromosomes

[bobc2]

Does each chromosome in a human cell contain one complete DNA molecule, so that there are 46 separate DNA molecules, one for each chromosome? Or does a single DNA molecule continue as an extended filament, running in and out of one chromosome, then proceeding to the next--eventually threading its way through all 46 chromosomes?

[canalon]

There are actually 92 separate DNA molecules.
Your first explanation is correct but 1 double helix of DNA is strictly speaking composed of 2 DNA molecules attached by hydrogen bonds (and a lot of them)

[bobc2]

Thank you very much, Canalon. However, I do question your notion that DNA should be counted as two molecules. The joining by hydrogen bonds qualifies the structure as a single molecule. By that reasoning you would always be looking at the vast number of single complex molecules that can be recognized as combinations of molecules.

I think I recall reading Watson's DNA book and his specifically refering to DNA as a single molecule. I'm certainly no expert on this stuff, so maybe someone else will jump in.

Still, I really appreciate you clearing up my confusion over the extent of the DNA double helix as it relates to the chromosomes.

[canalon]

Well that is how I was taught chemistry: molecules are composed of atoms with atomic bond. If you disagree, I have no problem with that, that is why I explained my self, rather than being my usually man of a few words when it comes to such questions.

[bobc2]

Canalon, we are definitely on the same page with your characterization of a molecule. In this instance I would say that it is the totality of all bonded atoms of the double helix that make DNA a single molecule.