1. DNA types: Division on the basis of position Chromosomal DNA Present on chromosome and is always part of choromosomal inheritance. It contains two nuclear DNA copies. Inherited both by male and female parents. It changes by 50% each generation. In human almost 3 billion nucleotides are present.

3. Plasmid DNA: Extra-chromosomal DNA molecule, capable of replicating independently. In many cases, it is circular and double-stranded. Plasmids are considered transferable genetic elements, or "replicons“. Plasmids have much less base pairs than chromosomes. Plasmids are rarely organized by chaperone proteins. Plasmids are easily transferred. Plasmids usually contain non-essential genes. Plasmids function can be lost or gained without harming the organism. Plasmids are usually found in "lower" organisms.

5. Mitochondrial DNA Mitochondria are eneergy producing machines. In humans, mitochondrial DNA spans about 16,500 DNA building blocks (base pairs). Mitochondrial DNA contains 37 genes, all of which are essential for normal mitochondrial function. Thirteen of these genes provide instructions for making enzymes involved in oxidative phosphorylation. The remaining genes provide instructions for making molecules called transfer RNA (tRNA) and ribosomal RNA (rRNA).

6. Mitochondrial DNA Mitochondrial DNA possesses 100s to 1000s of copies of DNA and pass only from mother parent during sexual reproduction. In case of human almost 16500 nucleotides are present in mtDNA. USES mtDNA is useful for forensic cases when nuclear DNA is insufficient. Each mitochondria contain 1 to 10 mtDNA. mtDNA useful for tracing one's direct maternal line (mother, maternal grandmother, maternal great- grandmother, etc).

8. Autosomal DNA Autosomal DNA is the type of DNA responsible for most physical characteristics. Autosomal DNA is inherited by sons and daughters from both parents. Autosomal Chromosomes are found in the nucleus of most of the cells in our body. One copy is of each pair inherited from our biological mother, and the other copy is from our biological father.

11. Y-DNA Y-DNA is a type of DNA that is only carried by men, who inherit it from their fathers. Y-DNA is particularly useful for tracing one's direct paternal line (father, paternal grandfather, etc.). Y-DNA it changes slowly from generation to generation, and in most societies, the surname of the father is also inherited by his sons.

13. Division on the basis of structure and funtion A-DNA A-form of DNA is right-handed, but every 2.3 nm makes a turn and there are 11 base pairs per turn.

14. B-DNA The most common form of DNA in living organisms. Double helix twists in a right-hand direction. B-DNA posses almost 10 bp per turn. the helix makes a turn every 3.4 nm, and the distance between two neighboring base pairs is 0.34 nm. In a solution with higher salt concentrations or with alcohol added, the DNA structure may change to an A form.

16. Z-DNA Because its bases seem to zigzag. Z DNA is left-handed. One turn spans 4.6 nm, comprising 12 base pairs. The DNA molecule with alternating G-C sequences in alcohol or high salt solution tends to have such structure.

18. cDNA (Clonal or complementary DNA) complementary DNA (cDNA) is DNA synthesized from a mature mRNA template.DNAmRNA cDNA is often used to clone eukaryotic genes in prokaryotes.eukaryoticgenesprokaryotes cDNA is most often synthesized from mature (fully spliced) mRNA using the enzyme reverse transcriptase.reverse transcriptase cDNA is produced from fully transcribed mRNA found in the nucleus and therefore contains only the expressed genes of an organism.mRNA cDNA is used to describe libraries of genetic information which is then used for testing pharmcuticals.