Yes, they are formed just before a cell replicates.

That statement is accurate to a degree. The nucleus of a cell technically contains chromosomes. But those chromosomes are in their decompressed form, called chromatin. It's just a double strand of DNA.

The 3 metres is an approximation. And no, the length is cumulative. Since we have 23 chromosomes and 1 strand of DNA will form 1 chromosome, I would assume there are 23 separate lengths of DNA. Instead of referring to it as a molecule you should refer to it as a protein (nit-picking).

I may have confused myself with the centromere. It`s either the centromere or centrosome that holds the two copies of a chromosome together. They have similar names, sue me for getting it wrong. I`m pretty sure that whatever it is that holds the two copies together is a protein. And no, proteins cannot be organells by themselves.

Yes the red dot is the centrosome/ centromere.

Hope that helps.

Yes, they are formed just before a cell replicates.

That statement is accurate to a degree. The nucleus of a cell technically contains chromosomes. But those chromosomes are in their decompressed form, called chromatin. It's just a double strand of DNA.

They are still chromosomes throughout the cell cycle (whether they are condensed or not) and the DNA is always packaged into chromatin. Chromatin is any DNA that is associated with histones (and some other proteins). A chromosome is two single strands of DNA that make up one double stranded piece of DNA in the cell.

They are still chromosomes throughout the cell cycle (whether they are condensed or not) and the DNA is always packaged into chromatin. Chromatin is any DNA that is associated with histones (and some other proteins). A chromosome is two single strands of DNA that make up one double stranded piece of DNA in the cell.

Yes this is right, but I was tryin not to confuse him. DNA is technically always a part of a chromosome, but when I was referring to a chromosome I meant the structure in general.

flatplat: Yea I noticed theres some big differences between prokaryotes and eukaryotes. These microorganisms interest me more than eukaryotes but I have to start learning somewhere so I'm gonna gain a good understanding of animal cells first.

Fair enough. :) But you do realize you're staring with the more complicated ones, right?

Well there are eukaryotic micoorganisms too, but they are generally more complex than bacteria.

Actually...not quite true. Viruses don't have DNA - they use RNA as their genetic material.

Viruses are NOT considered 'cells' of any sort...but that doesn't mean they aren't alive.

im pretty sure viruses have DNA, and retro viruses have RNA

Viruses can have DNA or RNA, single stranded or double stranded. Retroviruses are RNA viruses that use a reverse transcriptase to synthesize DNA from their RNA.

if you want to nitpick, here are some addendums

are virus alive?
depends on what your definition of life is. lots of scientists still debate on it

dna is not a protein. not sure where you got this.
dna is a polymer made of subunits called nucleotides.
protein is a polymer made of subunits called amino acids.

chromatin is not just a double strand of dna.
chromatin is a complex of dna and proteins (mainly histones). chromatin is what chromosome is made of

chromatin is not the decompressed form of chromosomes.
chromaTIN may take on a "compressed" form and it may also take on a "decompressed" form.
the compressed form is called heterochromatin. decompressed is called euchromatin.
i dont study bacteria so i dont know if this is the same thing for those guys..

whoever said "3m long dna"=> you meant to say 3m long chromosome


whatever real pua said is the truth

To understand what a chromosome is you need to understand how a cell stores genetic information. Within the nucleus of a cell, when a cell is not in the process of mitosis (replication), the genetic information , or DNA is uncoiled. Think of it as a giant ball of string, just unwound and floating around. When the cell enters its replication cycle it condenses the DNA into single chromosomes (23 in humans). To do this the DNA strand is wrapped around a protein complex called histones which then supercoil around themselves. This greatly condenses the DNA to the point where it can by seen under microscopes. At this point the supercoiled DNA looks a bit like a hot dog. Just a cylinder. To replicate properly the single chromosome replicates its self and takes on the classic X configuration, joined in the centre by a protein called a centrosome. In essence a chromosome is just like a spool. Our cells configure DNA into these structures to make it easier to move around. Think about trying to move 100 metres of string while it was unwound. Now think about how easy it would be if that string was wound around something. Cells are amazing things when you consider that if you stretched out all the DNA in a single cell it would form a thin fibre about 3 metres in length.


/rant.

ask and ye shall recieve

The cell replicates DNA during inter phase. Mitoses is cell replication. Also, if the cell went into mitosis with 23 single chromosomes, well, it wouldn't be a pretty sight. It enters mitosis with 46 replicated chromosomes. Two cells with 46 un-replicated chromosomes are the result.

A virus is something that hijacks a cell for use as it's own "factory", which then burst's releasing more of said virus, which repeat the process.