How many DNA strands does a chromosome have?

[scilearner]

Ok this seems like a simple question but when I checked I get so confused. Please use these terms to answer my question.

 

1 DNA molecule- This means a double helix (2 strands)

1 DNA strand- This means when you break the double helix and one separate strand

 

I thought one chromatid contain 1 DNA strand and 2 chromatids make a chromosome and 1 DNA molecule.

 

So in a diploid cell you have 46 DNA molecules or 92 strands. Is this wrong?

 

EDIT: Oh wait I know why I don't understand this. Chromatid also contains a DNA molecule right. When the cell is replicating each chromosome has 2 dna molecules and when it is not it only has one.

 

So when the cell is not reproducing there are 46 DNA molecules

and when it is there are 92 DNA molecules is that right?

Edited March 22, 2010 by scilearner

[Mr Skeptic]

The chromosome is a single double-stranded double helix, made of two DNA molecules hydrogen-bonded to each other. We are diploid, and we have 23 pairs of chromosomes, for a total of 46 chromosomes. Each chromosome is double stranded. A cell that is partway through reproducing will have twice as much (92 chromosomes), but a cell that reproduced via meiosis (an egg or sperm) will only have 23 chromosomes. So you could have a cell with 184 DNA molecules and one with 46 DNA molecules, though normally your cells have 92 DNA molecules.

[scilearner]

The chromosome is a single double-stranded double helix, made of two DNA molecules hydrogen-bonded to each other.

 

Thanks a lot for your answer You mean 2 strands not molecules here right. I consider one dna molecule to be a double helix. So when the cell is not replicating it has 46 DNA molecules or 92 DNA strands.

[Mr Skeptic]

Well do consider that each DNA strand is covalently bonded together but only hydrogen bonded to its matching strand. Much like water has millions of covalently bonded H2O molecules that are hydrogen bonded to each other. No one considers water to be a gigantic molecule due to all that hydrogen bonding. However, the DNA strands bind more strongly to each other due to their sheer size, so maybe you could consider them one molecule. However, even simple heating will separate the DNA strands from each other without breaking the covalent bonds (this is done in PCR, a technique for copying DNA).

[CharonY]

Either a double or a single strand is considered a molecule, respectively. Each has different chemical properties.

[scilearner]

I see Thanks Mr Skeptic and CharonY