This article throws light upon the top six methods of DNA polymorphism of a genome. The methods are: 1. RFLP 2. RAPD 3. OAF 4. AP-PCR 5. AFLP 6. SSR.
DNA Polymorphism of a Genome: Method # 1.
Restriction fragment length polymorphism. It is non-PCR based technique where genomic DNA is digested with restriction enzyme(s). The whole genetic material is cut at specific nucleotide sequences. The digest is put on electrophoreses blotted on a membrane and labelled with probe. Polymorphism in the hybridization pattern indicates the genetic difference between individuals.
DNA Polymorphism of a Genome: Method # 2.
Random amplified polymorphic DNA. It is PCR based genome characterization techniques. Single short oligonucleotide (9-12 bases) is used as primers for PCR amplification of genomic DNAs. Genomic DNA from two different individuals produces different amplification patterns and can be used for molecular characterization of individuals.
DNA Polymorphism of a Genome: Method # 3.
DNA amplification fingerprinting. It is similar to RAPD with difference that primer is shorter of (5-8) nucleotide sequence and used in higher concentration.
DNA Polymorphism of a Genome: Method # 4.
Arbitrarily primed polymerase chain reaction. These patterns are generated by employing single primers of 10-50 nucleotide bases length in PCR of genomic DNA.
DNA Polymorphism of a Genome: Method # 5.
Amplified fragment length polymorphism. This method is based on PCR amplification of genomic restriction fragments generated by specific restriction enzymes and oligonucleotide adapters of few nucleotide bases.
DNA is cut with restriction enzymes and double standard oligonucleotide adapters are joined to the ends of DNA fragments. Sets of restriction fragments are selectively amplified by labeled primers. The amplified products are separated on gel and screened using autoradiography.
DNA Polymorphism of a Genome: Method # 6.
Simple sequence repeats. This is also known as microsatellites. These are tandemly arranged repeats of mono-, di-, tri-, tetra- and pentanudeotides with different lengths of repeat motifs.
A. STMS: Sequence tagged micro-satellite sites
B. SNP: Single or simple nucleotide polymorphism
C. A pheromone is a small molecule secritereted by one mating type of organisms in order to interact with a member of the opposite mating type.
D. Cybrids or Cytoplasmic hybrids: Hybrids produced using nucleolus of one parent cell and cytoplasm of both the cell are called Cybrids. It involves m the fusion of a normal protoplast of one species with protoplast having inactivated nucleus of another species.
E. DNA replicase – DNA-synthesizing enzyme required specifically for replication.
F. Molecular scissors used in genetic engineering – Restriction endonuclease
G. Enzymes that attack bonds in DNA – DNAases
H. Explant is an excised fragment of a tissue or an organ used to start tissue culture.
I. Genetic map is map of genome showing relative positions of genes and or markers on chromosomes.
J. Gene pyramiding is technique of combining 2 or more major genes.
K. Genomics is science of identifying the sequence of DNA in species. They are complete set of chromosomes found in the gamete of true diploid (True diploid are individual with two set of chromosomes).
L. Germplasm is genetic background of a species.
M. Gene cloning is the process of synthesizing multiple copies of a particular DNA sequence using a bacterial cell or another organism as a host. It is used in genetic engineering as cloning.
N. Gene library is random collection cloned fragments in a vector that ideally includes all the genetic information of that species; For example, wheat, rice etc.
O. Gene cluster is a group of adjacent genes that are identical or related.
P. Map unit – The distance between two genes that recombine with a frequency of 1 %.
Q. Plasmid is an independent, double standard, closed circular, self-replicating autonomous molecule of DNA, existing in cells as extra chromosomal genomes or units, i.e. Pbr322, pACYC, Psc101, Co1E1 etc.