The DNA

DNA is a long polymer of deoxyribonucleotides. It is an acidic substance
present in nucleus. DNA was first identified by Friedrich Meischer in 1869.
He named it as "Nuclein". Altmann found these substances to be acidic in
nature, hence he named it nucliec acid.

The length of DNA is usually defined as number of nucleotides or a pair of
nucleotide referred to as base pairs (bp) present in it. This also is the
characteristic of an organism.


For e.g.,

Organisms	Genetic material	Number of nucleotides or bp
Fhai-X174 Bacteriophage	ssDNA, circular	5386 bases
Lamda Phage	dsDNA, Linear	48502 bp
Escherichia coli	dsDNA, circular	4.6 x 106 bp
Haploid Human Genome	dsDNA, Linear	3.3 x 109 bp

Occurrence of DNA
It is an acidic substance first isolated from nucleus of pus cells.
In eukaryotes, DNA occurs inside nucleus and two types of semi-autonomous cell organelle, mitochondria and plastids (e.g., chloroplasts).

Name of the DNA	Location inside the cells	Feature
Nuclear DNA	Inside the Nucleus	Nuclear DNA is associated with histone protiens to form chromatin fibres.
Organelle DNA	Inside semi-autonomous cell organelle	Organelle DNA is without Histone protiens (naked DNA).
Chromosomal DNA	Naked DNA embedded in prokaryotic cytoplasm.	DNA may be folded with the help of RNA and polyamines.
Plasmids	Prokaryotic cytoplasm.	Extranuclear or extra-chromosomal small circular DNA.

Check out more types of DNA here : DNA types.
Check out next post for :-
~ What are Nucleotides?
~ What are base pairs (bp)?