DNA: Deoxyribonucleic acid.
Between 2.2 and 2.6 nm wide. A double helix--a twisted ladder. Alternating sugars and phosphates as the outside of the ladder with four base-types connected in the middle with hydrogen bonds, thus making the rungs of the ladder.
The bases in the middle are Adenine h-bonded to thymine or guanine h-bonded to cytosine--always a purine attached to a pyrimidine.
Use and Storage of DNA
So, how does this DNA stuff work? Well, basically the pattern of the four bases designate certain sequences as genes; the basic function of a gene is to produce proteins. So basically, DNA guides development by dictating the proteins that are produced by cells.
Most of DNA is dormant--simply in-between sequences that are not used as genes at all. So, how is DNA used? Well, DNA is used to create RNA, which is used to create proteins. In this process, RNA copies and translates DNA through a process called transcription. So, if the nucleus of the cell is like the hard drive of a computer, then DNA is all of the little data files that designate what actions a computer takes.
So, how is DNA kept? Like, does the cell have a refrigerator or pantry or something? Basically, DNA is kept in the nucleus in conglomerations called chromosomes. The double helix, DNA, is again about 2 nm in length. It is wrapped around a set of proteins called histones. There are basically 5 histones. Histone 1 (which is not actually necessary for DNA to function properly and is only used to help compact DNA), histone 2A, histone 2B, histone 3, and histone 4--here referred to as H1, H2A, H2B, H3, and H4. Two units of each of the four H2-H4s combine to form a structure called the nucleosome.
When DNA is not compacted (when the cell is not undergoing mitosis), DNA is generally not visible. Sometimes, though, it can be seen under the microscope as what appears to be beads on a string.
In this form, the DNA strings (including the nucleosome beads) are about 10 nm in width. During mitosis, DNA is more compact. It is still in a string form, but the strings are folded in a certain way. It is not known for certain how the nucleosome string packs together, but when it does, it is about 30 nm wide.
These 30 nm fibers make up the coils of the condensed chromosome. When chromosomes are in their condensed form, they look like an X, which will be broken apart during mitosis as the chromosome is broken into two sister chromatids. The final chromosome is about 1400 nm, each sister chromatid being about 700 nm in width.
Here is a summation of the structure of the chromosome:
Belief
I believe in the decency of man. I believe in peace. I believe in equality. We as humans only have this one existence. Let's use it, explore it, love it.
(BTW, I wrote all of this. I took the images from wikipedia or a google search. So. Hope it was coherent and that you liked it.)