Human mind is always curious to know about things which are hidden. It is his nature to explore things and observe that what is the composition of the thing and what are its functions. Human genome was also a mystery for the people until scientists mapped it and determined different functions and expressions of genes. It was a very unique project of its type because scientists were going to unravel and discover the entire genetic makeup of the human body. It brought many social and ethical issues and many people criticized the mapping of the human genome.
Human genome project was suggested by a scientist Renato Dulbecco who wanted to map the whole genome to identify and locate the positions of the genes and what functions they perform. US department of energy also gave the idea of mapping human genome as many issues were being raised against the exposure of human body to radiations and chemicals. People were getting exposed to the atomic bombs and many mutations were occurring within their genomes which were resulting in cancers and other dangerous diseases. It resulted in the need of mapping the genome.
Goals of human genome project:-
When the human genome project started, scientists wanted to achieve following goals.
1) Identification of all the 30,000 genes present in the DNA of human body.
2) Determination of the sequences of chemical bases on which DNA structure is made.
3) Storage of the obtained information into the databases.
4) Development of the tools which will be concerned with data analysis.
5) Deal with the certain ethical and social issues regarding the mapping of human genome.
Process of human genome project:-
Human genome is determined with first mapping of the genes and then the characterization of the chromosomes. For example;
Strategies of mapping:-
When the sequencing of the human genome is concerned maps are needed for this purpose that is physical maps. They are the series of pieces of DNA which are overlapped. When the chemical characteristics of DNA have to be determined then physical maps are used. The benefit of mapping is that it divides the chromosomes into fragments so that the characterization of the chromosomal fragments becomes easy and it can be combined with the respective chromosomal locations.
Genetic markers are of great significance in the mapping of the genome. They are pieces of DNA but do not contain any genes. They enable the researchers to identify the person using a DNA sample. The genetic markers should be polymorphic so that they can be used in the genome mapping of different individuals. Polymorphism means the variation of the sequencing in the DNA. Change occurs in the sequencing of the DNA after every 300 to 500 base pairs. These markers are responsible for the creation of different characteristics in the human body like eye color, blood type etc. the genetic marker which is used mostly in the sequencing of DNA is RFLP that is restriction fragment length polymorphism.
Restriction enzymes are used to cut the DNA molecule into short pieces. They re isolated from the bacteria and cut the DNA at specific sites. There are some restriction enzymes which cut the DNA after short intervals generating very large fragments, the sequences of which are difficult to determine but in most of the cases, restriction enzymes cut the DNA into small fragments generating large number of small fragments.
Strategies of Sequencing:-
The physical map is actually the complete sequence of DNA which determines all the base pairs located on each chromosome. When the map is completed, it enables the scientists to determine the function of different genes and will give information about the human biology. Medical researchers can take information about the genes which are responsible for hereditary diseases from this mapping.
Using recombinant DNA technology to perform the process of cloning is performed on the pieces of the chromosomes which are isolated with the help of restriction enzymes. These fragments re then joined with the carriers or in other words with the vectors. These vectors are inserted into a host suitable for this purpose. The foreign DNA divides along with the host's DNA making many copies of the similar DNA. Bacteria are best suited for the insertion and cloning of the foreign genes. In some cases, yeast and mammalian cells re also used.
Polymerase chain Reaction:-
PCR is another method of cloning the small fragment of DNA molecule. In this process a polymerase enzyme is used which creates the complementary strand to the strand which is inserted in PCR for cloning. First the mixture is heated so that the double stranded DNA gets separated and then it is cooled down to bring the complementary bases on the separated strands. The process of heating and cooling continues and new copies of DNA molecule keep generating.
When the DNA molecule is amplified, now sequencing becomes easy. For this purpose, two processes can be used that is Maxim and Gilbert method and Sanger method. Both the methods can determine the sequences of DNA strands by using gel electrophoresis method in which the strands are separated into fragments and electric current is passed to separate the fragments according to their size. The fragments which contain even one different base pair can be separated.
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