Give an account of the methods used in sequencing the human genome.

Explanation

Sequencing of humen genome has made it possible to understend the link between various genes and their functions . If there are any gene defacts that defect that express as disorders or that increase the susceptibility of an individual to a disease then specific gene therepies can be worked out
Methodologies of humen genome sequencing
The methods involve two major approaches
(i) Expressed Sequence Tags (ESTs) This method focusses on identifying all the genes that are expressed as RNA .
(ii) Sequence annotation It is an apperoach of simply sequencing the whole set of genome that contains all the coding and non-coding sequence, and later assigning different regions in the sequence with functions .
For sequencing, first the total DNA from cell is i.e., solated and broken down in relatively small sizes as fragments.
There DNA fragments are cloned in suitable host using suitable vectors. When becteria is used as vactor , they are called Bacterial Artificial Chromosomes (BAC) and when yeast is used as vector, they are called Yeast Artifical Chromosomes (YACs).
Frederick Sanger developed a principle according to which the fragments of DNA are sequenced by automated DNA sequences.
On the basis of overlapping regions on DNA fragment, these sequences are arranged accordingly . For alignment of these sequences, specialised computer-based programmes were developed.
Finally, the genetic and physical maps of the genome were constructed by collecting information about cartian repetitive DNA sequences and DNA polymorphism, based on endonuclease recognition sites.