Genome sequencing is the process of determining the nucleic acid sequence and precise order of nucleotides in genome. It includes any method or technology that is used to determine the order of the four bases: adenine, guanine, cytosine, and thymine. It is a simple process in which the whole genome is broken into pieces, sequencing the pieces and then reassembling these pieces in a proper order to reach at the sequence of the whole genome.
DNA sequencing methods were first developed more than 20 years ago with the publication of two approaches to sequencing methodology that became known as Sanger sequencing and Maxim-Gilbert sequencing, which involved chemical degradation of end-radio-labeled DNA fragments. Both methods relied on four-lane, highresolution polyacrylamide gel electrophoresis to separate the labeled fragment and allow the base sequence to be read in a staggered ladder-like fashion.
The phi X 174 (or ΦX174) bacteriophage is a single-stranded DNA virus that infects Escherichia coli, and the first DNA-based genome to be sequenced. This work was completed by Fred Sanger and his team in 1977. Completion of the sequence marked a significant turning point in DNA sequencing because it was achieved with no prior genetic profile knowledge of the virus.
Advantages of genomic sequencing
In principle, full genome sequencing can provide the raw nucleotide sequence of an individual organism's DNA. However, further analysis must be performed to provide the biological or medical meaning of this sequence, such as how this knowledge can be used to help prevent disease.
helping scientists find genes much more easily and quickly
deciphering code of life
typing micro-organisms
detecting of mutations
identifying Human halotypes
designating polymorphisms
helps in the knowledge how the genome as a whole works, how genes work together to direct the growth, development and maintenance of an entire organism
finding of the regulatory regions
detect a wide range of variants
size of genomes for comparison
used in medical diagnostics and forensics
identifying regions of DNA associated with particular features, including specific diseases or increased susceptibility to specific diseases
understanding gene expression and how different genes interact
identification of substances, individuals and species
other genetic technologies such as gene therapy, genealogy research, plant and animal breeding and genetic modification.
It requires breaking the DNA of the genome into many smaller pieces, sequencing the pieces, and assembling the sequences into a single long "consensus." However, new methods that have been developed over the past two decades, genome sequencing is now much faster and less expensive than it was during the Human. Modern sequencing equipment uses the principles of the Sanger technique.
Factors that determine sequencing methods are;
Genome size
Chromosomal structure
Repeat content and character
Desired end product
Genome sequencing methods
Various methods of DNA sequencing are enlisted here;
Maxam and Gilbert method
Chain termination method
Semiautomated method
Automated method
Pyrosequencing
The whole-genome shotgun sequencing method
Clone by the clone sequencing method
Next-generation sequencing method
