Question 7: Give an account of the methods used in sequencing the human genome.
Answer:
Human genome Sequencing has made it possible to understand the link between various genes and their functions. If there are any gene found defected, is expressed as disorders or increases the susceptibility of an individual to a disease then specific gene therapies can be applied or used.
Methodologies of human genome sequencing:
- Expressed Sequence Tags (ESTs): This method focusses in identifying all the genes that are expressed as RNA.
- Sequence annotation: It is an process of simply sequencing the whole set of genome which contains all the coding and non- coding sequences and later assigning different regions in the sequence with the specific functions.
For sequencing, firstly the total DNA from cell, i.e., isolated and broken down in relatively small sizes as fragments. Then, DNA fragments are cloned in suitable host using suitable vectors. When bacteria is used as vector, they are called Bacterial Artificial Chromosome (BAC) and when yeast is used as vector, they are known as Yeast Artificial Chromosome (YACs).
Frederick Sanger described a principle according to which, the DNA fragments are sequenced by automated DNA sequences. On the basis of overlapping regions on fragmented DNA, these sequences are arranged accordingly. For alignment of these sequences, specialized computer based programs were developed.
Finally, the genetic and physical maps of the genome were constructed by collecting information or we can say on the base of data collection, certain repetitive DNA sequences and DNA polymorphism, based on endonuclease recognition sites.
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